docs: def power_factor(self):
          """
          Power factor of load
  
          Parameters
          -----------
          power_factor : :obj:`float`
              Ratio of real power to apparent power.
  
          Returns
          --------
          :obj:`float`
              Ratio of real power to apparent power. If power factor is not set
              it is retrieved from the network config object depending on the
              grid level the load is in.
  
          """
          if self._power_factor is None:
              if isinstance(self.grid, MVGrid):
                  self._power_factor = self.grid.network.config[
                      'reactive_power_factor']['mv_load']
              elif isinstance(self.grid, LVGrid):
                  self._power_factor = self.grid.network.config[
                      'reactive_power_factor']['lv_load']
          return self._power_factor