code: def on_key_press(self, event):
      if event.text == " ":
          self.index = (self.index + 1) % (len(self.markers.symbols))
          self.markers.symbol = self.markers.symbols[self.index]
          self.update()
      elif event.text == "s":
          self.markers.scaling = (
              "fixed" if self.markers.scaling != "fixed" else "scene"
          )
          self.update()
  
file_path: vispy/examples/basics/visuals/markers.py
imports: import numpy
  from vispy import app, visuals
  from vispy.visuals.transforms import STTransform
label_desc: Use image node_id 5 for calling the Canvas obj's underlying member method code with example usage: obj.on_key_press(event) without return types