class UserProxyAgent(BaseChatAgent):
    def __init__(self, name: str) -> None:
        super().__init__(name, "A human user.")

    @property
    def produced_message_types(self) -> List[type[ChatMessage]]:
        return [TextMessage, StopMessage, HandoffMessage]

    async def on_messages(
        self, messages: Sequence[ChatMessage], cancellation_token: CancellationToken
    ) -> Response:
        user_input = await asyncio.get_event_loop().run_in_executor( None, input, "User: ")

        # Find the last HandOffMessage targeting the user to determine who to hand off to.
        last_handoff_source = None
        for message in reversed(messages):
            if isinstance(message, HandoffMessage) and message.target == self.name:
                last_handoff_source = message.source
                break

        text_message = TextMessage(content=user_input, source=self.name)
        handoff_message = HandoffMessage(
            content="Handoff back to agent",
            source=self.name,
            target=last_handoff_source,
        )
        return Response(chat_message=text_message, inner_messages=[handoff_message])

    async def on_reset(self, cancellation_token: CancellationToken) -> None:
        self._last_handoff_source = None