def __init__(self, parent, target_cls):
        if target_cls <= parent._clslevel:
            parent.update_subclass(target_cls)
        self._exec_once = False
        self.parent_listeners = parent._clslevel[target_cls]
        self.parent = parent
        self.name = parent.name
        self.listeners = collections.deque()
        self.propagate = set()
dataset/ETHPy150Open zzzeek/sqlalchemy/lib/sqlalchemy/event/attr.py/_ListenerCollection.__init__/operator `not in` -> `<=`