          self.colourmaps = ["Reds", "Blues", "Greens", "Purples", "Oranges",
                             "Greys", "copper", "summer", "bone"]
          self.lines = list()
          self.toolbar = None
          self.fig = plt.figure(figsize=(4, 4), dpi=75)
          self.ax1 = self.fig.add_subplot(1, 1, 1)
          self.plotcanvas = FigureCanvasTkAgg(self.fig, self)
  
          self.initiate_graph()
          self.update_plot(initiate=True)
 
</s> remove class DisplayOptionalPage(DisplayPage):
 </s> add class DisplayOptionalPage(DisplayPage):  # pylint: disable=too-many-ancestors </s> remove class DisplayPage(ttk.Frame):
 </s> add class DisplayPage(ttk.Frame):  # pylint: disable=too-many-ancestors </s> remove         plt.subplots_adjust(left=0.100,
                            bottom=0.100,
                            right=0.95,
                            top=0.95,
                            wspace=0.2,
                            hspace=0.2)
 </s> add         self.fig.subplots_adjust(left=0.100,
                                 bottom=0.100,
                                 right=0.95,
                                 top=0.95,
                                 wspace=0.2,
                                 hspace=0.2)
        self.fig = Figure(figsize=(4, 4), dpi=75)

          self.colourmaps = ["Reds", "Blues", "Greens", "Purples", "Oranges",
                             "Greys", "copper", "summer", "bone"]
          self.lines = list()
          self.toolbar = None
        self.fig = Figure(figsize=(4, 4), dpi=75)

          self.ax1 = self.fig.add_subplot(1, 1, 1)
          self.plotcanvas = FigureCanvasTkAgg(self.fig, self)
  
          self.initiate_graph()
          self.update_plot(initiate=True)
keep keep keep keep replace keep keep keep keep keep
 bigfix: RuntimeWarning: More than 20 figures have been opened. 
lib/gui/display_graph.py