Required functionality.

def find_by_index(self, cls, index_name, value):
        """Required functionality."""
        table_name = cls.get_table_name()
        index_name_vals = [(index_name, value)]

        final_results = []
        for db_result in read_by_indexes(table_name, index_name_vals):
            obj = cls.from_data(db_result['value'])
            final_results.append(obj)

        return final_results