code: def on_draw(self, event):
      self.context.clear("white")
      self.points.draw()
  
file_path: vispy/examples/basics/visuals/custom_visual.py
imports: from __future__ import division
  import numpy
  from vispy import app
  from vispy.gloo import VertexBuffer
  from vispy.visuals import Visual
  from vispy.visuals.transforms import STTransform
label_desc: Use image node_id 4 for calling the Canvas obj's underlying member method code with example usage: obj.on_draw(event) without return types