code: def psi(i, j, k, offset=(25, 25, 50)):
      x = i - offset[0]
      y = j - offset[1]
      z = k - offset[2]
      th = np.arctan2(z, (x**2 + y**2) ** 0.5)
      r = (x**2 + y**2 + z**2) ** 0.5
      a0 = 1
      ps = (
          (1.0 / 81.0)
          * 1.0
          / (6.0 * np.pi) ** 0.5
          * (1.0 / a0) ** (3 / 2)
          * (r / a0) ** 2
          * np.exp(-r / (3 * a0))
          * (3 * np.cos(th) ** 2 - 1)
      )
      return ps
  
imports: import sys
  import numpy
  from vispy import app, scene
label_desc: Use image node_id 1 for calling a global function with example usage: psi(i, j, k, offset) and returns: ps