docs: def make_log_metric(level=logging.INFO, msg="%d items in %.2f seconds"):
      """Make a new metric function that logs at the given level
  
      :arg int level: logging level, defaults to ``logging.INFO``
      :arg string msg: logging message format string, taking ``count`` and ``elapsed``
      :rtype: function
      """
      def log_metric(name, count, elapsed):
          log_name = 'instrument.{}'.format(name) if name else 'instrument'
          logging.getLogger(log_name).log(level, msg, count, elapsed)
      return log_metric