code: public static BigQueryFileFormat getFileFormat(Configuration conf) throws IOException {
      // Ensure the BigQuery output information is valid.
      String fileFormatName =
          ConfigurationUtil.getMandatoryConfig(conf, BigQueryConfiguration.OUTPUT_FILE_FORMAT_KEY);
  
      return BigQueryFileFormat.fromName(fileFormatName);
    }
docs: Gets the stored output {@link BigQueryFileFormat} in the configuration.
  
  @param conf the configuration to reference the keys from.
  @return the stored output {@link BigQueryFileFormat} in the configuration.
  @throws IOException if file format value is missing from the configuration.