def append_conversation(
    conversation: Conversation,
    history: list[Conversation],
    placeholder: DeltaGenerator | None = None,
) -> None:
    """
    Append a conversation piece into history, meanwhile show it in a new markdown block
    """
    history.append(conversation)
    conversation.show(placeholder)

    Append a conversation piece into history, meanwhile show it in a new markdown block
    
demo/composite_demo/src/main.py