def stopped(reason):
    """
        The flow of data from this L{ITube}'s input has ceased; this
        corresponds to L{IDrain.flowStopped}.

        @note: L{ITube} I{has} no notification corresponding to
            L{IFount.stopFlow}, since it has no control over whether additional
            data will be synthesized / processed by I{its} fount, there's no
            useful work it can do.

        @return: The same as L{ITube.received}; values returned (or yielded) by
            this method will be propagated before the L{IDrain.flowStopped}
            notification to the downstream drain.
        @rtype: same as L{ITube.received}
        """
