code: def update(self):
      self.im.set_data(self.X[:, :, self.index])
      self.ax.set_title(
          f"Use scroll wheel to navigate\nindex {self.index}"
      )
      self.im.axes.figure.canvas.draw()
  
imports: import matplotlib.pyplot
  import numpy
label_desc: Use image node_id 3 for calling the IndexTracker obj's underlying member method code with example usage: obj.update() without return types