code: def update():
      global p4, z, index
      index -= 1
      p4.setData(z=z[index % z.shape[0]])
  
imports: import numpy
  import pyqtgraph
  import pyqtgraph.opengl
  from pyqtgraph.Qt import QtCore
label_desc: Use image node_id 1 for calling a global function with example usage: update() without return types