docs: def show_plot_methods(self):
          """Print the plotmethods of this instance"""
          print_func = PlotterInterface._print_func
          if print_func is None:
              print_func = six.print_
          s = "\n".join(
              "%s\n    %s" % t for t in six.iteritems(self._plot_methods))
          return print_func(s)