docs: def options(self, parser, env=os.environ):
          """Register commandline options."""
          super(TimerPlugin, self).options(parser, env)
  
          # timer top n
          parser.add_option(
              "--timer-top-n",
              action="store",
              default="-1",
              dest="timer_top_n",
              help=(
                  "When the timer plugin is enabled, only show the N tests that "
                  "consume more time. The default, -1, shows all tests."
              ),
          )
  
          parser.add_option(
              "--timer-json-file",
              action="store",
              default=None,
              dest="json_file",
              help=(
                  "Save the results of the timing and status of each tests in "
                  "said Json file."
              ),
          )
  
          _time_units_help = ("Default time unit is a second, but you can set "
                              "it explicitly (e.g. 1s, 500ms)")
  
          # timer ok
          parser.add_option(
              "--timer-ok",
              action="store",
              default=1,
              dest="timer_ok",
              help=(
                  "Normal execution time. Such tests will be highlighted in "
                  "green. {units_help}.".format(units_help=_time_units_help)
              ),
          )
  
          # time warning
          parser.add_option(
              "--timer-warning",
              action="store",
              default=3,
              dest="timer_warning",
              help=(
                  "Warning about execution time to highlight slow tests in "
                  "yellow. Tests which take more time will be highlighted in "
                  "red. {units_help}.".format(units_help=_time_units_help)
              ),
          )
  
          # Windows + nosetests does not support colors (even with colorama).
          if not IS_NT:
              parser.add_option(
                  "--timer-no-color",
                  action="store_true",
                  default=False,
                  dest="timer_no_color",
                  help="Don't colorize output (useful for non-tty output).",
              )
  
          # timer filter
          parser.add_option(
              "--timer-filter",
              action="store",
              default=None,
              dest="timer_filter",
              help="Show filtered results only (ok,warning,error).",
          )
  
          # timer fail
          parser.add_option(
              "--timer-fail",
              action="store",
              default=None,
              dest="timer_fail",
              choices=('warning', 'error'),
              help="Fail tests that exceed a threshold (warning,error)",
          )