code: def _normalize(self, x_y):
      x, y = x_y
      w, h = float(self.size[0]), float(self.size[1])
      return x / (w / 2.0) - 1.0, y / (h / 2.0) - 1.0
  
file_path: vispy/examples/demo/gloo/signals.py
imports: from vispy import gloo
  from vispy import app
  import numpy
  import math
label_desc: Use image node_id 4 for calling the Canvas obj's underlying member method code with example usage: obj._normalize(x_y) and returns: unknown,  unknown