def load_field_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._field_configs:
            self._field_configs[file_id] = self._reader.read_yaml_file(
                'field_config_%s.yml' % file_id)

        return self._field_configs[file_id]