docs: def save_model(self, model, meta_data=None, index_fields=None):
          """
          saves the model instance to riak
  
          Args:
              meta (dict): JSON serializable meta data for logging of save operation.
                  {'lorem': 'ipsum', 'dolar': 5}
              index_fields (list): Tuple list for secondary indexing keys in riak (with 'bin' or 'int').
                  [('lorem','bin'),('dolar','int')]
          :return:
          """
          return self.adapter.save_model(model, meta_data, index_fields)