def METHOD_NAME(self, connection: SendConnection):
    if connection.session_id in self._sessions:
        return
    self._sessions[connection.session_id] = _SessionCopier(connection)
    connection.task_group.start_soon(
        self._run_session,
        connection.session_id,
        name=f"pubsub copier for sid {connection.session_id}",
    )