Python の双方向ハッシュ テーブルを使用すると、どのようにして効率的なキーベースと値ベースのインデックス作成が可能になるのでしょうか?

<code class="python">class bidict(dict):
    def __init__(self, *args, **kwargs):
        super(bidict, self).__init__(*args, **kwargs)
        self.inverse = {}
        for key, value in self.items():
            self.inverse.setdefault(value, []).append(key)

    def __setitem__(self, key, value):
        if key in self:
            self.inverse[self[key]].remove(key)
        super(bidict, self).__setitem__(key, value)
        self.inverse.setdefault(value, []).append(key)

    def __delitem__(self, key):
        self.inverse.setdefault(self[key], []).remove(key)
        if self[key] in self.inverse and not self.inverse[self[key]]:
            del self.inverse[self[key]]
        super(bidict, self).__delitem__(key)</code>

<code class="python">bd = bidict({'a': 1, 'b': 2})

print(bd)  # {'a': 1, 'b': 2}
print(bd.inverse)  # {1: ['a'], 2: ['b']}

bd['c'] = 1  # Two keys have the same value
print(bd)  # {'a': 1, 'c': 1, 'b': 2}
print(bd.inverse)  # {1: ['a', 'c'], 2: ['b']}</code>