Add parent reference to embedded containers (#1711)

Allows embedded containers to access data from other embeddeds or the
main status.

miio/devicestatus.py

@@ -39,6 +39,7 @@ def __new__(metacls, name, bases, namespace, **kwargs):
         cls._sensors: Dict[str, SensorDescriptor] = {}
         cls._settings: Dict[str, SettingDescriptor] = {}
 
+        cls._parent: Optional["DeviceStatus"] = None
         cls._embedded: Dict[str, "DeviceStatus"] = {}
 
         descriptor_map = {
@@ -117,6 +118,7 @@ def embed(self, other: "DeviceStatus"):
         other_name = str(other.__class__.__name__)
 
         self._embedded[other_name] = other
+        other._parent = self  # type: ignore[attr-defined]
 
         for name, sensor in other.sensors().items():
             final_name = f"{other_name}__{name}"

miio/tests/test_devicestatus.py

@@ -270,6 +270,7 @@ def sub_sensor(self):
     main.embed(sub)
     sensors = main.sensors()
     assert len(sensors) == 2
+    assert sub._parent == main
 
     assert getattr(main, sensors["main_sensor"].property) == "main"
     assert getattr(main, sensors["SubStatus__sub_sensor"].property) == "sub"