code: def value_count(self, key):
          
          check_not_none(key, "key can't be none")
          return self._encode_invoke(transactional_multi_map_value_count_codec, key=self._to_data(key))
docs: Transactional implementation of :func:`MultiMap.value_count(key)
          <hazelcast.proxy.multi_map.MultiMap.value_count>`
  
          :param key: (object), the key whose number of values is to be returned.
          :return: (int), the number of values matching the given key in the multimap.