code: protected void setStagingFileGroup()
        throws IOException {
      Preconditions.checkArgument(this.fs.exists(this.stagingFile),
          String.format("Staging output file %s does not exist", this.stagingFile));
      if (this.group.isPresent()) {
        HadoopUtils.setGroup(this.fs, this.stagingFile, this.group.get());
      }
    }
docs: Set the group name of the staging output file.
  
  @throws IOException if it fails to set the group name