docs: def plot(self, phi, r, **kwargs):
          """Add a data series to the plot.
  
          :param phi: array containing phi-values, should be in degrees
                      (or radians).
          :param r: array containing r-values.
  
          For further options see the plot function of the super class.
  
          """
          if self.use_radians:
              phi = np.degrees(phi)
          super(PolarPlot, self).plot(phi, r, **kwargs)