docs: def onscroll(self, event):
          """Action to be taken when an event is triggered.
  
          Event is scroll of the mouse's wheel. This leads to changing the temporal frame displayed.
  
          :param event: Scroll of mouse wheel
          """
          if event.button == 'up':
              self.ind = (self.ind + 1) % self.slices
          else:
              self.ind = (self.ind - 1) % self.slices
          self.update()