code: def on_draw(self, event):
      c = 0.5 + math.sin(math.pi * time.time()) / 2.0
      self.context.clear([c] * 3)
      self.update()
  
imports: import math
  import time
  from vispy import app
label_desc: Use image node_id 2 for calling the Canvas obj's underlying member method code with example usage: obj.on_draw(event) without return types