code: def data(self):
      return self._data
  
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 2 for calling the SignalsVisual obj's underlying member method code with example usage: obj.data() and returns: self