def stream_by_id(self, dst_id):
        """
        Return the :class:`Stream` that should be used to communicate with
        `dst_id`. If a specific route for `dst_id` is not known, a reference to
        the parent context's stream is returned.
        """
        return (
            self._stream_by_id.get(dst_id) or
            self._stream_by_id.get(mitogen.parent_id)
        )
Return the :class:`Stream` that should be used to communicate with
        `dst_id`. If a specific route for `dst_id` is not known, a reference to
        the parent context's stream is returned.