docs: def set_bgcolor(self, color):
          """set color for background of plot"""
          self.bgcolor = color
          for ax in self.canvas.figure.get_axes():
              if matplotlib.__version__ < '2.0':
                  ax.set_axis_bgcolor(color)
              else:
                  ax.set_facecolor(color)
          if callable(self.theme_color_callback):
              self.theme_color_callback(color, 'bg')