code: def _normalize(self, x_y):
      x, y = x_y
      w, h = float(self.width), float(self.height)
      return x / (w / 2.0) - 1.0, y / (h / 2.0) - 1.0
  
imports: import numpy
  import math
  from vispy import gloo, app, scene
  from vispy.visuals import Visual
  from vispy.visuals.shaders import Function, Variable
  from vispy.visuals.transforms import TransformSystem, BaseTransform
  from vispy.util.profiler import Profiler
label_desc: Use image node_id 3 for calling the PanZoomCanvas obj's underlying member method code with example usage: obj._normalize(x_y) and returns: unknown,  unknown