def contains_key(self, key):
check_not_none(key, "<STR_LIT>")<EOL>key_data = self._to_data(key)<EOL>return self._encode_invoke_on_key(multi_map_contains_key_codec, key_data, key=key_data,<EOL>thread_id=thread_id())<EOL>
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.