(self, callback)
Sets a callback to invoke on cancel.

    Asks that the given callback be called when the RPC is canceled.  The
    callback will always be called exactly once.  If the RPC completes without
    being canceled, the callback will be called after completion.  If the RPC
    has already been canceled when NotifyOnCancel() is called, the callback
    will be called immediately.

    NotifyOnCancel() must be called no more than once per request.
Sets a callback to invoke on cancel.
Sets a callback to invoke on cancel .
def NotifyOnCancel(self, callback):
    """Sets a callback to invoke on cancel.

    Asks that the given callback be called when the RPC is canceled.  The
    callback will always be called exactly once.  If the RPC completes without
    being canceled, the callback will be called after completion.  If the RPC
    has already been canceled when NotifyOnCancel() is called, the callback
    will be called immediately.

    NotifyOnCancel() must be called no more than once per request.
    """
    raise NotImplementedError
def NotifyOnCancel ( self , callback ) : raise NotImplementedError