public String getFirstResult(final Argument arg) {
    final String[] all = getResult(arg);
    if (all == null) {
      return null;
    } else {
      return all[0];
    }
  }
Convenience method to return the first value of the first instance of the command line argument
values for the specified argument.

@param arg argument to query
@return first parameter of the first list of parameters supplied
extensions/geode-modules-session/src/main/java/org/apache/geode/modules/session/installer/args/ArgumentValues.java