def load_transaction_config(self, file_id):
        """
        Loads the configuration fields file for the id.

        :param file_id: the id for the field
        :return: the fields configuration
        """
        if file_id not in self._transaction_configs:
            self._transaction_configs[file_id] = self._reader.read_config_file(
                'transaction_config_%s.cml' % file_id)

        return self._transaction_configs[file_id]