'Entry point for triggering the binding from save signals.'

@classmethod
def pre_change_receiver(cls, instance, action):

    if (action == CREATE):
        group_names = set()
    else:
        group_names = set(cls.group_names(instance))
    if (not hasattr(instance, u'_binding_group_names')):
        instance._binding_group_names = {}
    instance._binding_group_names[cls] = group_names
