code: def zoom_in(self):
          
          index = self._zoom_factors.index(self._zoom_factor)
          if index + 1 == len(self._zoom_factors):
              # Already zoomed in all the way
              return
          self._zoom_factor = self._zoom_factors[index + 1]
          if self._zoom_factors.index(self.zoom_factor) + 1 == len(self._zoom_factors):
              self._button_zoom_in.config(state=tk.DISABLED)
          self._button_zoom_out.config(state=tk.NORMAL)
          self.draw_timeline()
docs: Increase zoom factor and redraw TimeLine