Clarify typed Python event examples

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

python/README.md

@@ -25,8 +25,10 @@ python chat.py
 
 ```python
 import asyncio
+from typing import cast
+
 from copilot import CopilotClient
-from copilot.session import PermissionHandler
+from copilot.generated.session_events import AssistantMessageData
 
 async def main():
     # Client automatically starts on enter and cleans up on exit
@@ -38,7 +40,7 @@ async def main():
 
             def on_event(event):
                 if event.type.value == "assistant.message":
-                    print(event.data.content)
+                    print(cast(AssistantMessageData, event.data).content)
                 elif event.type.value == "session.idle":
                     done.set()
 
@@ -57,7 +59,10 @@ If you need more control over the lifecycle, you can call `start()`, `stop()`, a
 
 ```python
 import asyncio
+from typing import cast
+
 from copilot import CopilotClient
+from copilot.generated.session_events import AssistantMessageData
 from copilot.session import PermissionHandler
 
 async def main():
@@ -74,7 +79,7 @@ async def main():
 
     def on_event(event):
         if event.type.value == "assistant.message":
-            print(event.data.content)
+            print(cast(AssistantMessageData, event.data).content)
         elif event.type.value == "session.idle":
             done.set()
 
@@ -333,7 +338,15 @@ Enable streaming to receive assistant response chunks as they're generated:
 
 ```python
 import asyncio
+from typing import cast
+
 from copilot import CopilotClient
+from copilot.generated.session_events import (
+    AssistantMessageData,
+    AssistantMessageDeltaData,
+    AssistantReasoningData,
+    AssistantReasoningDeltaData,
+)
 from copilot.session import PermissionHandler
 
 async def main():
@@ -350,20 +363,20 @@ async def main():
                 match event.type.value:
                     case "assistant.message_delta":
                         # Streaming message chunk - print incrementally
-                        delta = event.data.delta_content or ""
+                        delta = cast(AssistantMessageDeltaData, event.data).delta_content or ""
                         print(delta, end="", flush=True)
                     case "assistant.reasoning_delta":
                         # Streaming reasoning chunk (if model supports reasoning)
-                        delta = event.data.delta_content or ""
+                        delta = cast(AssistantReasoningDeltaData, event.data).delta_content or ""
                         print(delta, end="", flush=True)
                     case "assistant.message":
                         # Final message - complete content
                         print("\n--- Final message ---")
-                        print(event.data.content)
+                        print(cast(AssistantMessageData, event.data).content)
                     case "assistant.reasoning":
                         # Final reasoning content (if model supports reasoning)
                         print("--- Reasoning ---")
-                        print(event.data.content)
+                        print(cast(AssistantReasoningData, event.data).content)
                     case "session.idle":
                         # Session finished processing
                         done.set()

python/copilot/session.py

@@ -1128,9 +1128,11 @@ async def send_and_wait(
             Exception: If the session has been disconnected or the connection fails.
 
         Example:
+            >>> from typing import cast
+            >>> from copilot.generated.session_events import AssistantMessageData
             >>> response = await session.send_and_wait("What is 2+2?")
             >>> if response:
-            ...     print(response.data.content)
+            ...     print(cast(AssistantMessageData, response.data).content)
         """
         idle_event = asyncio.Event()
         error_event: Exception | None = None
@@ -1176,11 +1178,13 @@ def on(self, handler: Callable[[SessionEvent], None]) -> Callable[[], None]:
             A function that, when called, unsubscribes the handler.
 
         Example:
+            >>> from typing import cast
+            >>> from copilot.generated.session_events import AssistantMessageData, SessionErrorData
             >>> def handle_event(event):
-            ...     if event.type == "assistant.message":
-            ...         print(f"Assistant: {event.data.content}")
-            ...     elif event.type == "session.error":
-            ...         print(f"Error: {event.data.message}")
+            ...     if event.type.value == "assistant.message":
+            ...         print(f"Assistant: {cast(AssistantMessageData, event.data).content}")
+            ...     elif event.type.value == "session.error":
+            ...         print(f"Error: {cast(SessionErrorData, event.data).message}")
             >>> unsubscribe = session.on(handle_event)
             >>> # Later, to stop receiving events:
             >>> unsubscribe()
@@ -1801,10 +1805,12 @@ async def get_messages(self) -> list[SessionEvent]:
             Exception: If the session has been disconnected or the connection fails.
 
         Example:
+            >>> from typing import cast
+            >>> from copilot.generated.session_events import AssistantMessageData
             >>> events = await session.get_messages()
             >>> for event in events:
-            ...     if event.type == "assistant.message":
-            ...         print(f"Assistant: {event.data.content}")
+            ...     if event.type.value == "assistant.message":
+            ...         print(f"Assistant: {cast(AssistantMessageData, event.data).content}")
         """
         response = await self._client.request("session.getMessages", {"sessionId": self.session_id})
         # Convert dict events to SessionEvent objects