docs: def plot_residual_load(network):
      """ Plots residual load summed of all exisiting buses.
  
      Parameters
      ----------
      network : PyPSA network containter
      """
  
      renewables = network.generators[
          network.generators.carrier.isin(['wind_onshore', 'wind_offshore', 
                                           'solar', 'run_of_river',
                                           'wind'])]
      renewables_t = network.generators.p_nom[renewables.index] * \
          network.generators_t.p_max_pu[renewables.index].mul(
                  network.snapshot_weightings, axis=0)
      load = network.loads_t.p_set.mul(network.snapshot_weightings, axis=0).\
      sum(axis=1)
      all_renew = renewables_t.sum(axis=1)
      residual_load = load - all_renew
      plot = residual_load.plot(
          title = 'Residual load',
          drawstyle='steps',
          lw=2,
          color='red',
          legend=False)
      plot.set_ylabel("MW")
      # sorted curve
      sorted_residual_load = residual_load.sort_values(
          ascending=False).reset_index()
      plot1 = sorted_residual_load.plot(
              title='Sorted residual load',
              drawstyle='steps',
              lw=2,
              color='red',
              legend=False)
      plot1.set_ylabel("MW")