docs: def max_load(network, boundaries=[], filename=None, two_cb=False):
      
      """Plot maximum loading of each line. 
      
      Parameters
      ----------
      network: PyPSA network container
          Holds topology of grid including results from powerflow analysis
      filename: str or None
          Save figure in this direction
      boundaries: array
         Set boundaries of heatmap axis
      two_cb: bool
          Choose if an extra colorbar for DC-lines is plotted
      
      """
  
      cmap_line = plt.cm.jet
      cmap_link = plt.cm.jet
      array_line = [['Line'] * len(network.lines), network.lines.index]
      array_link = [['Link'] * len(network.links), network.links.index]
  
      if network.lines_t.q0.empty:
          load_lines = pd.Series((abs(network.lines_t.p0).max(
                  ) / (network.lines.s_nom) * 100).data, index=array_line)
  
      else: load_lines = pd.Series(((network.lines_t.p0**2 +
                             network.lines_t.q0 ** 2).max().apply(sqrt)/
                             (network.lines.s_nom) * 100).data, index=array_line)
          
      load_links = pd.Series((abs(network.links_t.p0.max(
                  ) / (network.links.p_nom)) * 100).data, index=array_link)
  
      max_load = load_lines.append(load_links)
  
      ll = network.plot(
          line_colors=max_load,
          line_cmap={
              'Line': cmap_line,
              'Link': cmap_link},
          bus_sizes=0,
          title="Maximum of line loading",
          line_widths=2)
  
      if not boundaries:
          boundaries = [min(max_load), max(max_load)]
  
      v = np.linspace(boundaries[0], boundaries[1], 101)
  
      cb = plt.colorbar(ll[1], boundaries=v,
                        ticks=v[0:101:10])
  
      cb.set_clim(vmin=boundaries[0], vmax=boundaries[1])
  
      cb_Link = plt.colorbar(ll[2], boundaries=v,
                                 ticks=v[0:101:10])
      cb_Link.set_clim(vmin=boundaries[0], vmax=boundaries[1])
  
      if two_cb:
          # cb_Link.set_label('Maximum load of DC-lines %')
          cb.set_label('Maximum load of AC-lines %')
  
      else:
          cb.set_label('Maximum load in %')
      if filename is None:
          plt.show()
      else:
          plt.savefig(filename)
          plt.close()