code: public String getValue(Option option) {
          if (option == null) {
              return null;
          }
          String[] values = getValues(option);
          return (values == null ? null : values[0]);
      }
docs: Retrieve the first argument, if any, of this option.
  
  @param option the name of the option
  @return the value of the argument if option is set, and has an argument,
  otherwise {@code null}