core/src/main/java/com/twitter/elephantbird/mapred/output/DeprecatedOutputFormatWrapper.java
public static void setOutputFormat(Class<?> realOutputFormatClass, JobConf jobConf) {
    jobConf.setOutputFormat(DeprecatedOutputFormatWrapper.class);
    HadoopUtils.setClassConf(jobConf, CLASS_CONF_KEY, realOutputFormatClass);
  }
public static void setOutputFormat(Class<?> realOutputFormatClass, JobConf jobConf) {
    jobConf.setOutputFormat(DeprecatedOutputFormatWrapper.class);
    HadoopUtils.setClassConf(jobConf, CLASS_CONF_KEY, realOutputFormatClass);
  }
Sets jobs output format to {@link DeprecatedOutputFormatWrapper} and stores
supplied real {@link OutputFormat} class name in job configuration.
This configuration is read on the remote tasks to instantiate actual
OutputFormat correctly.