def _observers_for_notification(self, ntype, sender):
keys = (<EOL>(ntype,sender),<EOL>(ntype, None),<EOL>(None, sender),<EOL>(None,None)<EOL>)<EOL>obs = set()<EOL>for k in keys:<EOL><INDENT>obs.update(self.observers.get(k, set()))<EOL><DEDENT>return obs<EOL>
Find all registered observers that should recieve notification