'Send signal from sender to all connected receivers.
If any receiver raises an error, the error propagates back through send,
terminating the dispatch loop, so it is quite possible to not have all
receivers called if a raises an error.
Arguments:
sender
The sender of the signal Either a specific object or None.
named
Named arguments which will be passed to receivers.
Returns a list of tuple pairs [(receiver, response), ... ].'

def send(self, sender, **named):

    responses = []
    if (not self.receivers):
        return responses
    for receiver in self._live_receivers(_make_id(sender)):
        response = receiver(signal=self, sender=sender, **named)
        responses.append((receiver, response))
    return responses
