code: @Override
      void dump_i(final int indent_level) {
  	for (int i = 0; i < indent_level; i++) {
  	    System.out.print("  ");
  	}
  	System.out.println("|- Group: " + get_name() + " [" + get_size_i(true) + ":" + get_size_i(false) + "]");
  	final Iterator it = elements.iterator();
  	while (it.hasNext()) {
  	    ((GroupElement) it.next()).dump_i(indent_level + 1);
  	}
      }
docs: Dump group - access limited to package Group