diff --git a/playwright/async_api.py b/playwright/async_api.py
index b20e91001..1dba5976e 100644
--- a/playwright/async_api.py
+++ b/playwright/async_api.py
@@ -28,6 +28,10 @@
 from playwright.browser_context import BrowserContext as BrowserContextImpl
 from playwright.browser_server import BrowserServer as BrowserServerImpl
 from playwright.browser_type import BrowserType as BrowserTypeImpl
+from playwright.cdp_session import CDPSession as CDPSessionImpl
+from playwright.chromium_browser_context import (
+    ChromiumBrowserContext as ChromiumBrowserContextImpl,
+)
 from playwright.console_message import ConsoleMessage as ConsoleMessageImpl
 from playwright.dialog import Dialog as DialogImpl
 from playwright.download import Download as DownloadImpl
@@ -647,7 +651,7 @@ def __init__(self, obj: JSHandleImpl):
         super().__init__(obj)
 
     async def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """JSHandle.evaluate
 
@@ -676,7 +680,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """JSHandle.evaluateHandle
 
@@ -1034,7 +1038,7 @@ async def selectOption(
             typing.List[str],
             typing.List["ElementHandle"],
             typing.List[SelectOption],
-        ],
+        ] = None,
         timeout: int = None,
         noWaitAfter: bool = None,
     ) -> typing.List[str]:
@@ -1336,7 +1340,7 @@ async def evalOnSelector(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """ElementHandle.evalOnSelector
 
@@ -1374,7 +1378,7 @@ async def evalOnSelectorAll(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """ElementHandle.evalOnSelectorAll
 
@@ -1699,7 +1703,7 @@ async def frameElement(self) -> "ElementHandle":
         return mapping.from_impl(await self._impl_obj.frameElement())
 
     async def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """Frame.evaluate
 
@@ -1729,7 +1733,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """Frame.evaluateHandle
 
@@ -1878,7 +1882,7 @@ async def evalOnSelector(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Frame.evalOnSelector
 
@@ -1916,7 +1920,7 @@ async def evalOnSelectorAll(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Frame.evalOnSelectorAll
 
@@ -2334,7 +2338,7 @@ async def selectOption(
             typing.List[str],
             typing.List["ElementHandle"],
             typing.List[SelectOption],
-        ],
+        ] = None,
         timeout: int = None,
         noWaitAfter: bool = None,
     ) -> typing.List[str]:
@@ -2556,7 +2560,7 @@ async def waitForFunction(
         self,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
         timeout: int = None,
         polling: typing.Union[int, Literal["raf"]] = None,
     ) -> "JSHandle":
@@ -2640,7 +2644,7 @@ def url(self) -> str:
         return mapping.from_maybe_impl(self._impl_obj.url)
 
     async def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """Worker.evaluate
 
@@ -2668,7 +2672,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """Worker.evaluateHandle
 
@@ -2704,7 +2708,11 @@ def __init__(self, obj: SelectorsImpl):
         super().__init__(obj)
 
     async def register(
-        self, name: str, source: str = "", path: str = None, contentScript: bool = False
+        self,
+        name: str,
+        source: str = None,
+        path: str = None,
+        contentScript: bool = None,
     ) -> NoneType:
         """Selectors.register
 
@@ -2714,9 +2722,9 @@ async def register(
         ----------
         name : str
             Name that is used in selectors as a prefix, e.g. `{name: 'foo'}` enables `foo=myselectorbody` selectors. May only contain `[a-zA-Z0-9_]` characters.
-        source : str
+        source : Optional[str]
             Script that evaluates to a selector engine instance.
-        contentScript : bool
+        contentScript : Optional[bool]
             Whether to run this selector engine in isolated JavaScript environment. This environment has access to the same DOM, but not any JavaScript objects from the frame's scripts. Defaults to `false`. Note that running as a content script is not guaranteed when this engine is used together with other registered engines.
         """
         return mapping.from_maybe_impl(
@@ -3198,7 +3206,7 @@ async def dispatchEvent(
         )
 
     async def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """Page.evaluate
 
@@ -3230,7 +3238,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """Page.evaluateHandle
 
@@ -3264,7 +3272,7 @@ async def evalOnSelector(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Page.evalOnSelector
 
@@ -3303,7 +3311,7 @@ async def evalOnSelectorAll(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Page.evalOnSelectorAll
 
@@ -4281,7 +4289,7 @@ async def selectOption(
             typing.List[str],
             typing.List["ElementHandle"],
             typing.List[SelectOption],
-        ],
+        ] = None,
         timeout: int = None,
         noWaitAfter: bool = None,
     ) -> typing.List[str]:
@@ -4505,7 +4513,7 @@ async def waitForFunction(
         self,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
         timeout: int = None,
         polling: typing.Union[int, Literal["raf"]] = None,
     ) -> "JSHandle":
@@ -4913,7 +4921,7 @@ async def clearPermissions(self) -> NoneType:
         """
         return mapping.from_maybe_impl(await self._impl_obj.clearPermissions())
 
-    async def setGeolocation(self, geolocation: typing.Dict) -> NoneType:
+    async def setGeolocation(self, geolocation: typing.Dict = None) -> NoneType:
         """BrowserContext.setGeolocation
 
         Sets the context's geolocation. Passing `null` or `undefined` emulates position unavailable.
@@ -5133,6 +5141,85 @@ def expect_page(
 mapping.register(BrowserContextImpl, BrowserContext)
 
 
+class CDPSession(AsyncBase):
+    def __init__(self, obj: CDPSessionImpl):
+        super().__init__(obj)
+
+    async def send(self, method: str, params: typing.Dict = None) -> typing.Dict:
+        """CDPSession.send
+
+        Parameters
+        ----------
+        method : str
+            protocol method name
+        params : Optional[typing.Dict]
+            Optional method parameters
+
+        Returns
+        -------
+        typing.Dict
+        """
+        return mapping.from_maybe_impl(
+            await self._impl_obj.send(method=method, params=params)
+        )
+
+    async def detach(self) -> NoneType:
+        """CDPSession.detach
+
+        Detaches the CDPSession from the target. Once detached, the CDPSession object won't emit any events and can't be used
+        to send messages.
+        """
+        return mapping.from_maybe_impl(await self._impl_obj.detach())
+
+
+mapping.register(CDPSessionImpl, CDPSession)
+
+
+class ChromiumBrowserContext(BrowserContext):
+    def __init__(self, obj: ChromiumBrowserContextImpl):
+        super().__init__(obj)
+
+    def backgroundPages(self) -> typing.List["Page"]:
+        """ChromiumBrowserContext.backgroundPages
+
+        Returns
+        -------
+        typing.List[Page]
+            All existing background pages in the context.
+        """
+        return mapping.from_impl_list(self._impl_obj.backgroundPages())
+
+    def serviceWorkers(self) -> typing.List["Worker"]:
+        """ChromiumBrowserContext.serviceWorkers
+
+        Returns
+        -------
+        typing.List[Worker]
+            All existing service workers in the context.
+        """
+        return mapping.from_impl_list(self._impl_obj.serviceWorkers())
+
+    async def newCDPSession(self, page: "Page") -> "CDPSession":
+        """ChromiumBrowserContext.newCDPSession
+
+        Parameters
+        ----------
+        page : Page
+            Page to create new session for.
+
+        Returns
+        -------
+        CDPSession
+            Promise that resolves to the newly created session.
+        """
+        return mapping.from_impl(
+            await self._impl_obj.newCDPSession(page=page._impl_obj)
+        )
+
+
+mapping.register(ChromiumBrowserContextImpl, ChromiumBrowserContext)
+
+
 class Browser(AsyncBase):
     def __init__(self, obj: BrowserImpl):
         super().__init__(obj)
diff --git a/playwright/browser.py b/playwright/browser.py
index 60d8f4058..fed3fb0c6 100644
--- a/playwright/browser.py
+++ b/playwright/browser.py
@@ -14,7 +14,7 @@
 
 import sys
 from types import SimpleNamespace
-from typing import Dict, List, Union
+from typing import TYPE_CHECKING, Dict, List, Union
 
 from playwright.browser_context import BrowserContext
 from playwright.connection import ChannelOwner, from_channel
@@ -27,15 +27,19 @@
 else:  # pragma: no cover
     from typing_extensions import Literal
 
+if TYPE_CHECKING:  # pragma: no cover
+    from playwright.browser_type import BrowserType
+
 
 class Browser(ChannelOwner):
 
     Events = SimpleNamespace(Disconnected="disconnected",)
 
     def __init__(
-        self, parent: ChannelOwner, type: str, guid: str, initializer: Dict
+        self, parent: "BrowserType", type: str, guid: str, initializer: Dict
     ) -> None:
         super().__init__(parent, type, guid, initializer)
+        self._browser_type = parent
         self._is_connected = True
         self._is_closed_or_closing = False
 
diff --git a/playwright/cdp_session.py b/playwright/cdp_session.py
new file mode 100644
index 000000000..0aad85106
--- /dev/null
+++ b/playwright/cdp_session.py
@@ -0,0 +1,39 @@
+# Copyright (c) Microsoft Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import Any, Dict
+
+from playwright.connection import ChannelOwner
+from playwright.js_handle import parse_result, serialize_argument
+
+
+class CDPSession(ChannelOwner):
+    def __init__(
+        self, parent: ChannelOwner, type: str, guid: str, initializer: Dict
+    ) -> None:
+        super().__init__(parent, type, guid, initializer)
+        self._channel.on("event", lambda params: self._on_event(params))
+
+    def _on_event(self, params: Any) -> None:
+        self.emit(params["method"], parse_result(params["params"]))
+
+    async def send(self, method: str, params: Dict = None) -> Dict:
+        payload = {"method": method}
+        if params:
+            payload["params"] = serialize_argument(params)["value"]
+        result = await self._channel.send("send", payload)
+        return parse_result(result)
+
+    async def detach(self) -> None:
+        await self._channel.send("detach")
diff --git a/playwright/chromium_browser_context.py b/playwright/chromium_browser_context.py
new file mode 100644
index 000000000..bc13fb54d
--- /dev/null
+++ b/playwright/chromium_browser_context.py
@@ -0,0 +1,66 @@
+# Copyright (c) Microsoft Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from types import SimpleNamespace
+from typing import Dict, List, Set
+
+from playwright.browser_context import BrowserContext
+from playwright.cdp_session import CDPSession
+from playwright.connection import ChannelOwner, from_channel
+from playwright.page import Page, Worker
+
+
+class ChromiumBrowserContext(BrowserContext):
+
+    Events = SimpleNamespace(
+        BackgroundPage="backgroundpage", ServiceWorker="serviceworker",
+    )
+
+    def __init__(
+        self, parent: ChannelOwner, type: str, guid: str, initializer: Dict
+    ) -> None:
+        super().__init__(parent, type, guid, initializer)
+
+        self._background_pages: Set[Page] = set()
+        self._service_workers: Set[Worker] = set()
+
+        self._channel.on(
+            "crBackgroundPage",
+            lambda params: self._on_background_page(from_channel(params["page"])),
+        )
+
+        self._channel.on(
+            "crServiceWorker",
+            lambda params: self._on_service_worker(from_channel(params["worker"])),
+        )
+
+    def _on_background_page(self, page: Page) -> None:
+        self._background_pages.add(page)
+        self.emit(ChromiumBrowserContext.Events.BackgroundPage, page)
+
+    def _on_service_worker(self, worker: Worker) -> None:
+        worker._context = self
+        self._service_workers.add(worker)
+        self.emit(ChromiumBrowserContext.Events.ServiceWorker, worker)
+
+    def backgroundPages(self) -> List[Page]:
+        return list(self._background_pages)
+
+    def serviceWorkers(self) -> List[Worker]:
+        return list(self._service_workers)
+
+    async def newCDPSession(self, page: Page) -> CDPSession:
+        return from_channel(
+            await self._channel.send("crNewCDPSession", {"page": page._channel})
+        )
diff --git a/playwright/element_handle.py b/playwright/element_handle.py
index c02e370bc..a53c44808 100644
--- a/playwright/element_handle.py
+++ b/playwright/element_handle.py
@@ -187,7 +187,7 @@ async def querySelectorAll(self, selector: str) -> List["ElementHandle"]:
         )
 
     async def evalOnSelector(
-        self, selector: str, expression: str, arg: Any = None, force_expr: bool = False
+        self, selector: str, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return parse_result(
             await self._channel.send(
@@ -202,7 +202,7 @@ async def evalOnSelector(
         )
 
     async def evalOnSelectorAll(
-        self, selector: str, expression: str, arg: Any = None, force_expr: bool = False
+        self, selector: str, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return parse_result(
             await self._channel.send(
diff --git a/playwright/frame.py b/playwright/frame.py
index 15882dcc5..58a5e7f18 100644
--- a/playwright/frame.py
+++ b/playwright/frame.py
@@ -180,7 +180,7 @@ async def frameElement(self) -> ElementHandle:
         return from_channel(await self._channel.send("frameElement"))
 
     async def evaluate(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         if not is_function_body(expression):
             force_expr = True
@@ -196,7 +196,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> JSHandle:
         if not is_function_body(expression):
             force_expr = True
@@ -242,7 +242,7 @@ async def dispatchEvent(
         )
 
     async def evalOnSelector(
-        self, selector: str, expression: str, arg: Any = None, force_expr: bool = False
+        self, selector: str, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return parse_result(
             await self._channel.send(
@@ -257,7 +257,7 @@ async def evalOnSelector(
         )
 
     async def evalOnSelectorAll(
-        self, selector: str, expression: str, arg: Any = None, force_expr: bool = False
+        self, selector: str, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return parse_result(
             await self._channel.send(
@@ -447,7 +447,7 @@ async def waitForFunction(
         self,
         expression: str,
         arg: Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
         timeout: int = None,
         polling: Union[int, Literal["raf"]] = None,
     ) -> JSHandle:
diff --git a/playwright/js_handle.py b/playwright/js_handle.py
index e57e319e2..21d27738d 100644
--- a/playwright/js_handle.py
+++ b/playwright/js_handle.py
@@ -40,7 +40,7 @@ def _on_preview_updated(self, preview: str) -> None:
         self._preview = preview
 
     async def evaluate(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         if not is_function_body(expression):
             force_expr = True
@@ -56,7 +56,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> "JSHandle":
         if not is_function_body(expression):
             force_expr = True
diff --git a/playwright/object_factory.py b/playwright/object_factory.py
index 6cdcd22b0..d4cd118ce 100644
--- a/playwright/object_factory.py
+++ b/playwright/object_factory.py
@@ -12,12 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Dict
+from typing import Any, Dict, cast
 
 from playwright.browser import Browser
 from playwright.browser_context import BrowserContext
 from playwright.browser_server import BrowserServer
 from playwright.browser_type import BrowserType
+from playwright.cdp_session import CDPSession
+from playwright.chromium_browser_context import ChromiumBrowserContext
 from playwright.connection import ChannelOwner
 from playwright.console_message import ConsoleMessage
 from playwright.dialog import Dialog
@@ -44,13 +46,22 @@ def create_remote_object(
     if type == "BindingCall":
         return BindingCall(parent, type, guid, initializer)
     if type == "Browser":
-        return Browser(parent, type, guid, initializer)
+        return Browser(cast(BrowserType, parent), type, guid, initializer)
     if type == "BrowserServer":
         return BrowserServer(parent, type, guid, initializer)
     if type == "BrowserType":
         return BrowserType(parent, type, guid, initializer)
     if type == "BrowserContext":
+        browser_name: str = ""
+        if isinstance(parent, Browser):
+            browser_name = parent._browser_type.name
+        if isinstance(parent, BrowserType):
+            browser_name = parent.name
+        if browser_name == "chromium":
+            return ChromiumBrowserContext(parent, type, guid, initializer)
         return BrowserContext(parent, type, guid, initializer)
+    if type == "CDPSession":
+        return CDPSession(parent, type, guid, initializer)
     if type == "ConsoleMessage":
         return ConsoleMessage(parent, type, guid, initializer)
     if type == "Dialog":
diff --git a/playwright/page.py b/playwright/page.py
index 4cfe5c7b3..38771fd8d 100644
--- a/playwright/page.py
+++ b/playwright/page.py
@@ -300,26 +300,26 @@ async def dispatchEvent(
         return await self._main_frame.dispatchEvent(**locals_to_params(locals()))
 
     async def evaluate(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return await self._main_frame.evaluate(expression, arg, force_expr=force_expr)
 
     async def evaluateHandle(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> JSHandle:
         return await self._main_frame.evaluateHandle(
             expression, arg, force_expr=force_expr
         )
 
     async def evalOnSelector(
-        self, selector: str, expression: str, arg: Any = None, force_expr: bool = False
+        self, selector: str, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return await self._main_frame.evalOnSelector(
             selector, expression, arg, force_expr=force_expr
         )
 
     async def evalOnSelectorAll(
-        self, selector: str, expression: str, arg: Any = None, force_expr: bool = False
+        self, selector: str, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         return await self._main_frame.evalOnSelectorAll(
             selector, expression, arg, force_expr=force_expr
@@ -661,7 +661,7 @@ async def waitForFunction(
         self,
         expression: str,
         arg: Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
         timeout: int = None,
         polling: Union[int, Literal["raf"]] = None,
     ) -> JSHandle:
@@ -792,10 +792,13 @@ def __init__(
         super().__init__(parent, type, guid, initializer)
         self._channel.on("close", lambda _: self._on_close())
         self._page: Optional[Page] = None
+        self._context: Optional["BrowserContext"] = None
 
     def _on_close(self) -> None:
         if self._page:
             self._page._workers.remove(self)
+        if self._context:
+            self._context._service_workers.remove(self)
         self.emit(Worker.Events.Close, self)
 
     @property
@@ -803,7 +806,7 @@ def url(self) -> str:
         return self._initializer["url"]
 
     async def evaluate(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> Any:
         if not is_function_body(expression):
             force_expr = True
@@ -819,7 +822,7 @@ async def evaluate(
         )
 
     async def evaluateHandle(
-        self, expression: str, arg: Any = None, force_expr: bool = False
+        self, expression: str, arg: Any = None, force_expr: bool = None
     ) -> JSHandle:
         return from_channel(
             await self._channel.send(
diff --git a/playwright/selectors.py b/playwright/selectors.py
index 5306d474e..e3f3d8aa9 100644
--- a/playwright/selectors.py
+++ b/playwright/selectors.py
@@ -16,6 +16,7 @@
 
 from playwright.connection import ChannelOwner
 from playwright.element_handle import ElementHandle
+from playwright.helper import Error
 
 
 class Selectors(ChannelOwner):
@@ -25,14 +26,21 @@ def __init__(
         super().__init__(parent, type, guid, initializer)
 
     async def register(
-        self, name: str, source: str = "", path: str = None, contentScript: bool = False
+        self,
+        name: str,
+        source: str = None,
+        path: str = None,
+        contentScript: bool = None,
     ) -> None:
+        if not source and not path:
+            raise Error("Either source or path should be specified")
         if path:
             with open(path, "r") as file:
                 source = file.read()
-        await self._channel.send(
-            "register", dict(name=name, source=source, contentScript=contentScript),
-        )
+        params: Dict = dict(name=name, source=source)
+        if contentScript:
+            params["contentScript"] = True
+        await self._channel.send("register", params)
 
     async def _createSelector(self, name: str, handle: ElementHandle) -> Optional[str]:
         return await self._channel.send(
diff --git a/playwright/sync_api.py b/playwright/sync_api.py
index 93bd205d8..3fcfb2982 100644
--- a/playwright/sync_api.py
+++ b/playwright/sync_api.py
@@ -27,6 +27,10 @@
 from playwright.browser_context import BrowserContext as BrowserContextImpl
 from playwright.browser_server import BrowserServer as BrowserServerImpl
 from playwright.browser_type import BrowserType as BrowserTypeImpl
+from playwright.cdp_session import CDPSession as CDPSessionImpl
+from playwright.chromium_browser_context import (
+    ChromiumBrowserContext as ChromiumBrowserContextImpl,
+)
 from playwright.console_message import ConsoleMessage as ConsoleMessageImpl
 from playwright.dialog import Dialog as DialogImpl
 from playwright.download import Download as DownloadImpl
@@ -659,7 +663,7 @@ def __init__(self, obj: JSHandleImpl):
         super().__init__(obj)
 
     def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """JSHandle.evaluate
 
@@ -692,7 +696,7 @@ def evaluate(
         )
 
     def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """JSHandle.evaluateHandle
 
@@ -1062,7 +1066,7 @@ def selectOption(
             typing.List[str],
             typing.List["ElementHandle"],
             typing.List[SelectOption],
-        ],
+        ] = None,
         timeout: int = None,
         noWaitAfter: bool = None,
     ) -> typing.List[str]:
@@ -1382,7 +1386,7 @@ def evalOnSelector(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """ElementHandle.evalOnSelector
 
@@ -1422,7 +1426,7 @@ def evalOnSelectorAll(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """ElementHandle.evalOnSelectorAll
 
@@ -1757,7 +1761,7 @@ def frameElement(self) -> "ElementHandle":
         return mapping.from_impl(self._sync(self._impl_obj.frameElement()))
 
     def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """Frame.evaluate
 
@@ -1791,7 +1795,7 @@ def evaluate(
         )
 
     def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """Frame.evaluateHandle
 
@@ -1946,7 +1950,7 @@ def evalOnSelector(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Frame.evalOnSelector
 
@@ -1986,7 +1990,7 @@ def evalOnSelectorAll(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Frame.evalOnSelectorAll
 
@@ -2423,7 +2427,7 @@ def selectOption(
             typing.List[str],
             typing.List["ElementHandle"],
             typing.List[SelectOption],
-        ],
+        ] = None,
         timeout: int = None,
         noWaitAfter: bool = None,
     ) -> typing.List[str]:
@@ -2666,7 +2670,7 @@ def waitForFunction(
         self,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
         timeout: int = None,
         polling: typing.Union[int, Literal["raf"]] = None,
     ) -> "JSHandle":
@@ -2754,7 +2758,7 @@ def url(self) -> str:
         return mapping.from_maybe_impl(self._impl_obj.url)
 
     def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """Worker.evaluate
 
@@ -2786,7 +2790,7 @@ def evaluate(
         )
 
     def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """Worker.evaluateHandle
 
@@ -2826,7 +2830,11 @@ def __init__(self, obj: SelectorsImpl):
         super().__init__(obj)
 
     def register(
-        self, name: str, source: str = "", path: str = None, contentScript: bool = False
+        self,
+        name: str,
+        source: str = None,
+        path: str = None,
+        contentScript: bool = None,
     ) -> NoneType:
         """Selectors.register
 
@@ -2836,9 +2844,9 @@ def register(
         ----------
         name : str
             Name that is used in selectors as a prefix, e.g. `{name: 'foo'}` enables `foo=myselectorbody` selectors. May only contain `[a-zA-Z0-9_]` characters.
-        source : str
+        source : Optional[str]
             Script that evaluates to a selector engine instance.
-        contentScript : bool
+        contentScript : Optional[bool]
             Whether to run this selector engine in isolated JavaScript environment. This environment has access to the same DOM, but not any JavaScript objects from the frame's scripts. Defaults to `false`. Note that running as a content script is not guaranteed when this engine is used together with other registered engines.
         """
         return mapping.from_maybe_impl(
@@ -3324,7 +3332,7 @@ def dispatchEvent(
         )
 
     def evaluate(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> typing.Any:
         """Page.evaluate
 
@@ -3360,7 +3368,7 @@ def evaluate(
         )
 
     def evaluateHandle(
-        self, expression: str, arg: typing.Any = None, force_expr: bool = False
+        self, expression: str, arg: typing.Any = None, force_expr: bool = None
     ) -> "JSHandle":
         """Page.evaluateHandle
 
@@ -3398,7 +3406,7 @@ def evalOnSelector(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Page.evalOnSelector
 
@@ -3439,7 +3447,7 @@ def evalOnSelectorAll(
         selector: str,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
     ) -> typing.Any:
         """Page.evalOnSelectorAll
 
@@ -4460,7 +4468,7 @@ def selectOption(
             typing.List[str],
             typing.List["ElementHandle"],
             typing.List[SelectOption],
-        ],
+        ] = None,
         timeout: int = None,
         noWaitAfter: bool = None,
     ) -> typing.List[str]:
@@ -4705,7 +4713,7 @@ def waitForFunction(
         self,
         expression: str,
         arg: typing.Any = None,
-        force_expr: bool = False,
+        force_expr: bool = None,
         timeout: int = None,
         polling: typing.Union[int, Literal["raf"]] = None,
     ) -> "JSHandle":
@@ -5121,7 +5129,7 @@ def clearPermissions(self) -> NoneType:
         """
         return mapping.from_maybe_impl(self._sync(self._impl_obj.clearPermissions()))
 
-    def setGeolocation(self, geolocation: typing.Dict) -> NoneType:
+    def setGeolocation(self, geolocation: typing.Dict = None) -> NoneType:
         """BrowserContext.setGeolocation
 
         Sets the context's geolocation. Passing `null` or `undefined` emulates position unavailable.
@@ -5355,6 +5363,85 @@ def expect_page(
 mapping.register(BrowserContextImpl, BrowserContext)
 
 
+class CDPSession(SyncBase):
+    def __init__(self, obj: CDPSessionImpl):
+        super().__init__(obj)
+
+    def send(self, method: str, params: typing.Dict = None) -> typing.Dict:
+        """CDPSession.send
+
+        Parameters
+        ----------
+        method : str
+            protocol method name
+        params : Optional[typing.Dict]
+            Optional method parameters
+
+        Returns
+        -------
+        typing.Dict
+        """
+        return mapping.from_maybe_impl(
+            self._sync(self._impl_obj.send(method=method, params=params))
+        )
+
+    def detach(self) -> NoneType:
+        """CDPSession.detach
+
+        Detaches the CDPSession from the target. Once detached, the CDPSession object won't emit any events and can't be used
+        to send messages.
+        """
+        return mapping.from_maybe_impl(self._sync(self._impl_obj.detach()))
+
+
+mapping.register(CDPSessionImpl, CDPSession)
+
+
+class ChromiumBrowserContext(BrowserContext):
+    def __init__(self, obj: ChromiumBrowserContextImpl):
+        super().__init__(obj)
+
+    def backgroundPages(self) -> typing.List["Page"]:
+        """ChromiumBrowserContext.backgroundPages
+
+        Returns
+        -------
+        typing.List[Page]
+            All existing background pages in the context.
+        """
+        return mapping.from_impl_list(self._impl_obj.backgroundPages())
+
+    def serviceWorkers(self) -> typing.List["Worker"]:
+        """ChromiumBrowserContext.serviceWorkers
+
+        Returns
+        -------
+        typing.List[Worker]
+            All existing service workers in the context.
+        """
+        return mapping.from_impl_list(self._impl_obj.serviceWorkers())
+
+    def newCDPSession(self, page: "Page") -> "CDPSession":
+        """ChromiumBrowserContext.newCDPSession
+
+        Parameters
+        ----------
+        page : Page
+            Page to create new session for.
+
+        Returns
+        -------
+        CDPSession
+            Promise that resolves to the newly created session.
+        """
+        return mapping.from_impl(
+            self._sync(self._impl_obj.newCDPSession(page=page._impl_obj))
+        )
+
+
+mapping.register(ChromiumBrowserContextImpl, ChromiumBrowserContext)
+
+
 class Browser(SyncBase):
     def __init__(self, obj: BrowserImpl):
         super().__init__(obj)
diff --git a/scripts/generate_api.py b/scripts/generate_api.py
index ab3cc4c1d..e355c9890 100644
--- a/scripts/generate_api.py
+++ b/scripts/generate_api.py
@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import inspect
 import re
 from types import FunctionType
 from typing import (  # type: ignore
@@ -31,6 +30,8 @@
 from playwright.browser_context import BrowserContext
 from playwright.browser_server import BrowserServer
 from playwright.browser_type import BrowserType
+from playwright.cdp_session import CDPSession
+from playwright.chromium_browser_context import ChromiumBrowserContext
 from playwright.console_message import ConsoleMessage
 from playwright.dialog import Dialog
 from playwright.download import Download
@@ -53,13 +54,13 @@ def process_type(value: Any, param: bool = False) -> str:
     value = re.sub(r"playwright\.[\w]+\.([\w]+)", r'"\1"', value)
     value = re.sub(r"typing.Literal", "Literal", value)
     if param:
-        value = re.sub(r"typing.Union\[([^,]+), NoneType\]", r"\1", value)
-        if "Union[Literal" in value:
-            value = re.sub(r"typing.Union\[(.*), NoneType\]", r"\1", value)
-        else:
-            value = re.sub(
-                r"typing.Union\[(.*), NoneType\]", r"typing.Union[\1]", value
-            )
+        value = re.sub(r"^typing.Union\[([^,]+), NoneType\]$", r"\1 = None", value)
+        value = re.sub(
+            r"typing.Union\[(Literal\[[^\]]+\]), NoneType\]", r"\1 = None", value
+        )
+        value = re.sub(
+            r"^typing.Union\[(.+), NoneType\]$", r"typing.Union[\1] = None", value
+        )
     return value
 
 
@@ -68,22 +69,11 @@ def signature(func: FunctionType, indent: int) -> str:
     tokens = ["self"]
     split = ",\n" + " " * indent
 
-    func_signature = inspect.signature(func)
     for [name, value] in hints.items():
         if name == "return":
             continue
         processed = process_type(value, True)
-        default_value = func_signature.parameters[name].default
-        if default_value is not func_signature.parameters[name].empty:
-            if isinstance(default_value, str):
-                default_value = '"' + default_value + '"'
-            elif isinstance(default_value, object):
-                default_value = str(default_value)
-            else:
-                raise ValueError(f"value {default_value} not recognized")
-            tokens.append(f"{name}: {processed} = {default_value}")
-        else:
-            tokens.append(f"{name}: {processed}")
+        tokens.append(f"{name}: {processed}")
     return split.join(tokens)
 
 
@@ -99,6 +89,8 @@ def arguments(func: FunctionType, indent: int) -> str:
             tokens.append(f"{name}=self._wrap_handler({name})")
         elif "typing.Any" in value_str or "Handle" in value_str:
             tokens.append(f"{name}=mapping.to_impl({name})")
+        elif re.match(r"<class 'playwright\.[\w]+\.[\w]+", value_str):
+            tokens.append(f"{name}={name}._impl_obj")
         else:
             tokens.append(f"{name}={name}")
     return split.join(tokens)
@@ -160,6 +152,8 @@ def return_value(value: Any) -> List[str]:
 from playwright.browser_context import BrowserContext as BrowserContextImpl
 from playwright.browser_server import BrowserServer as BrowserServerImpl
 from playwright.browser_type import BrowserType as BrowserTypeImpl
+from playwright.cdp_session import CDPSession as CDPSessionImpl
+from playwright.chromium_browser_context import ChromiumBrowserContext as ChromiumBrowserContextImpl
 from playwright.console_message import ConsoleMessage as ConsoleMessageImpl
 from playwright.dialog import Dialog as DialogImpl
 from playwright.download import Download as DownloadImpl
@@ -194,6 +188,8 @@ def return_value(value: Any) -> List[str]:
     BindingCall,
     Page,
     BrowserContext,
+    CDPSession,
+    ChromiumBrowserContext,
     Browser,
     BrowserServer,
     BrowserType,
diff --git a/tests/async/test_cdp_session.py b/tests/async/test_cdp_session.py
new file mode 100644
index 000000000..a8c09ced6
--- /dev/null
+++ b/tests/async/test_cdp_session.py
@@ -0,0 +1,78 @@
+# Copyright (c) Microsoft Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import asyncio
+
+import pytest
+
+from playwright import Error
+
+
+@pytest.mark.only_browser("chromium")
+async def test_should_work(page):
+    client = await page.context.newCDPSession(page)
+
+    await asyncio.gather(
+        client.send("Runtime.enable"),
+        client.send("Runtime.evaluate", {"expression": "window.foo = 'bar'"}),
+    )
+    foo = await page.evaluate("() => window.foo")
+    assert foo == "bar"
+
+
+@pytest.mark.only_browser("chromium")
+async def test_should_send_events(page, server):
+    client = await page.context.newCDPSession(page)
+    await client.send("Network.enable")
+    events = []
+    client.on("Network.requestWillBeSent", lambda event: events.append(event))
+    await page.goto(server.EMPTY_PAGE)
+    assert len(events) == 1
+
+
+@pytest.mark.only_browser("chromium")
+async def test_should_be_able_to_detach_session(page):
+    client = await page.context.newCDPSession(page)
+    await client.send("Runtime.enable")
+    eval_response = await client.send(
+        "Runtime.evaluate", {"expression": "1 + 2", "returnByValue": True}
+    )
+    assert eval_response["result"]["value"] == 3
+    await client.detach()
+    with pytest.raises(Error) as exc_info:
+        await client.send(
+            "Runtime.evaluate", {"expression": "3 + 1", "returnByValue": True}
+        )
+    assert "Target browser or context has been closed" in exc_info.value.message
+
+
+@pytest.mark.only_browser("chromium")
+async def test_should_not_break_page_close(browser):
+    context = await browser.newContext()
+    page = await context.newPage()
+    session = await page.context.newCDPSession(page)
+    await session.detach()
+    await page.close()
+    await context.close()
+
+
+@pytest.mark.only_browser("chromium")
+async def test_should_detach_when_page_closes(browser):
+    context = await browser.newContext()
+    page = await context.newPage()
+    session = await context.newCDPSession(page)
+    await page.close()
+    with pytest.raises(Error):
+        await session.detach()
+    await context.close()
diff --git a/tests/async/test_queryselector.py b/tests/async/test_queryselector.py
index 923e7cfde..cd6714ba2 100644
--- a/tests/async/test_queryselector.py
+++ b/tests/async/test_queryselector.py
@@ -133,8 +133,8 @@ async def test_selectors_register_should_handle_errors(selectors, page: Page, ut
     with pytest.raises(Error) as exc:
         await selectors.register("$", dummy_selector_engine_script)
     assert (
-        "Selector engine name may only contain [a-zA-Z0-9_] characters"
-        == exc.value.message
+        exc.value.message
+        == "Selector engine name may only contain [a-zA-Z0-9_] characters"
     )
 
     # Selector names are case-sensitive.