code: def get_required_arguments_metricnames(self):
      
      try:
        metricnames = self.get_arguments(constants.PARAM_METRICNAME)
        if not metricnames:
          raise tornado.web.MissingArgumentError(constants.PARAM_METRICNAME)
        return metricnames
      except tornado.web.MissingArgumentError as e:
        raise Exception(e.log_message)
docs: Helper function to get metricname arguments.
      Notice that it is get_argument"s" variation, which means that this can be repeated.
      Raises exception if argument is missing.
      Returns a list of metricname arguments