code: def find_by_index(self, cls, index_name, value):
          
          query_args = {
              index_name + '__eq': DynamoMappings.map_index_val(value),
              'index': gsi_name(index_name)
          }
  
          final_results = []
          for db_result in self.get_class_table(cls).query_2(**query_args):
              obj = cls.from_data(db_result['value'])
              final_results.append(obj)
  
          return final_results
docs: Required functionality.