code: def start_move(self, start):
      self.drag_reference = (
          start[0:2] - self.control_points.get_center()
      )
  
imports: import numpy
  from vispy import app, scene
  from vispy.color import Color
label_desc: Use image node_id 4 for calling the EditVisual obj's underlying member method code with example usage: obj.start_move(start) without return types