code: def update(self, ax):
      # Update the line
      lims = ax.viewLim
      if abs(lims.width - self.delta) > 1e-8:
          self.delta = lims.width
          xstart, xend = lims.intervalx
          self.line.set_data(*self.downsample(xstart, xend))
          ax.figure.canvas.draw_idle()
  
imports: import matplotlib.pyplot
  import numpy
label_desc: Use image node_id 3 for calling the DataDisplayDownsampler obj's underlying member method code with example usage: obj.update(ax) without return types