async def append_event(self, session: Session, event: Event) -> Event:
    """Appends an event to a session object."""
    if event.partial:
      return event
    self.__update_session_state(session, event)
    session.events.append(event)
    return event
Appends an event to a session object.
src/google/adk/sessions/base_session_service.py