+ """
+ A class that stores both a Mapping between keys and values and
+ also the inverse mapping between values and their keys to
+ allow for efficient lookups in either direction. Because it
+ is possible to have several keys with the same value, using
+ the inverse map returns a sequence of keys.
+
+ >>> d = BiDict()
+ >>> d['a'] = 1
+ >>> d['b'] = 2
+ >>> d['c'] = 2
+ >>> d['a']
+ 1
+ >>> d.inverse[1]
+ ['a']
+ >>> d.inverse[2]
+ ['b', 'c']
+ >>> len(d)
+ 3
+ >>> del d['c']
+ >>> len(d)
+ 2
+ >>> d.inverse[2]
+ ['b']
+
+ """
+ super().__init__(*args, **kwargs)