'Triggers the binding to possibly send to its group.'

@classmethod
def post_change_receiver(cls, instance, action, **kwargs):

    old_group_names = instance._binding_group_names[cls]
    if (action == DELETE):
        new_group_names = set()
    else:
        new_group_names = set(cls.group_names(instance))
    self = cls()
    self.instance = instance
    self.send_messages(instance, (old_group_names - new_group_names), DELETE, **kwargs)
    self.send_messages(instance, (old_group_names & new_group_names), UPDATE, **kwargs)
    self.send_messages(instance, (new_group_names - old_group_names), CREATE, **kwargs)
