chore(examples): add langchain-openai example from #58

examples/test_langchain_openai.py

@@ -0,0 +1,41 @@
+from langchain_openai import ChatOpenAI
+from pydantic.v1 import SecretStr
+
+import openai_responses
+from openai_responses import OpenAIMock
+
+
+@openai_responses.mock()
+def test_langchain_chat_openai_invoke(openai_mock: OpenAIMock):
+    openai_mock.chat.completions.create.response = {
+        "choices": [
+            {
+                "index": 0,
+                "finish_reason": "stop",
+                "message": {
+                    "content": "J'adore la programmation.",
+                    "role": "assistant",
+                },
+            }
+        ]
+    }
+
+    llm = ChatOpenAI(
+        name="My Custom Chatbot",
+        model="gpt-4o",
+        temperature=0,
+        max_tokens=None,
+        timeout=None,
+        max_retries=2,
+        api_key=SecretStr("sk-fake123"),
+    )
+
+    messages = [
+        (
+            "system",
+            "You are a helpful assistant that translates English to French. Translate the user sentence.",
+        ),
+        ("human", "I love programming."),
+    ]
+    ai_msg = llm.invoke(messages)
+    assert ai_msg.content == "J'adore la programmation."  # type: ignore