code: public static void setInputFormat(Class<?> realInputFormatClass, Job job) {
      job.setInputFormatClass(MapReduceInputFormatWrapper.class);
      setWrappedInputFormat(realInputFormatClass, HadoopCompat.getConfiguration(job));
    }
docs: Sets jobs input format to {@link MapReduceInputFormatWrapper} and stores
  supplied real {@link InputFormat} class name in job configuration.
  This configuration is read on the remote tasks to instantiate actual
  InputFormat correctly.