Determines whether this multimap contains an entry with the key.

        **Warning: This method uses __hash__ and __eq__ methods of binary form of the key, not the actual implementations
        of __hash__ and __eq__ defined in key's class.**

        :param key: (object), the specified key.
        :return: (bool), ``true`` if this multimap contains an entry for the specified key.

def contains_key(self, key):
        """
        Determines whether this multimap contains an entry with the key.

        **Warning: This method uses __hash__ and __eq__ methods of binary form of the key, not the actual implementations
        of __hash__ and __eq__ defined in key's class.**

        :param key: (object), the specified key.
        :return: (bool), ``true`` if this multimap contains an entry for the specified key.
        """
        check_not_none(key, "key can't be None")
        key_data = self._to_data(key)
        return self._encode_invoke_on_key(multi_map_contains_key_codec, key_data, key=key_data,
                                          thread_id=thread_id())