code: private void chgrp(AlluxioURI path, String group, boolean recursive)
        throws AlluxioException, IOException {
      SetAttributePOptions options =
          SetAttributePOptions.newBuilder().setGroup(group).setRecursive(recursive).build();
      mFileSystem.setAttribute(path, options);
      System.out.println("Changed group of " + path + " to " + group);
    }
docs: Changes the group for the directory or file with the path specified in args.
  
  @param path The {@link AlluxioURI} path as the input of the command
  @param group The group to be updated to the file or directory
  @param recursive Whether change the group recursively