code: protected static OptionParser getParser() {
              OptionParser parser = new OptionParser();
              // help options
              AdminParserUtils.acceptsHelp(parser);
              // required options
              parser.accepts(OPT_HEAD_META_CHECK, "metadata keys to be checked")
                    .withOptionalArg()
                    .describedAs("meta-key-list")
                    .withValuesSeparatedBy(',')
                    .ofType(String.class);
              AdminParserUtils.acceptsUrl(parser);
              return parser;
          }
docs: Initializes parser
  
  @return OptionParser object with all available options