code: def _gen_delta_per_sec(self, path, value_delta, time_delta, multiplier,
                             prettyname, device):
          
          if time_delta < 0:
              return
          value = (value_delta / time_delta) * multiplier
          # Only publish if there is any data.
          # This helps keep unused metrics out of Graphite
          if value > 0.0:
              self._replace_and_publish(path, prettyname, value, device)
docs: Calulates the difference between to point, and scales is to per second.