code: def gauge(self, slug, current_value):
          
          k = self._gauge_key(slug)
          self.r.sadd(self._gauge_slugs_key, slug)  # keep track of all Gauges
          self.r.set(k, current_value)
docs: Set the value for a Gauge.
  
          * ``slug`` -- the unique identifier (or key) for the Gauge
          * ``current_value`` -- the value that the gauge should display