def send(self, sender, **named):
responses = []<EOL>if not self.receivers:<EOL><INDENT>return responses<EOL><DEDENT>sender_id = _make_id(sender)<EOL>if sender_id not in self.sender_status:<EOL><INDENT>self.sender_status[sender_id] = {}<EOL><DEDENT>if self.sender_status[sender_id] == named:<EOL><INDENT>return responses<EOL><DEDENT>self.sender_status[sender_id] = named<EOL>for receiver in self._live_receivers(sender_id):<EOL><INDENT>response = receiver(signal=self, sender=sender, **named)<EOL>responses.append((receiver, response))<EOL><DEDENT>return responses<EOL>
Send signal from sender to all connected receivers *only if* the signal's
contents has changed.

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), ... ].