code: def Lab_to_XYZ(cobj, *args, **kwargs):
      
      illum = cobj.get_illuminant_xyz()
      xyz_y = (cobj.lab_l + 16.0) / 116.0
      xyz_x = cobj.lab_a / 500.0 + xyz_y
      xyz_z = xyz_y - cobj.lab_b / 200.0
  
      if math.pow(xyz_y, 3) > color_constants.CIE_E:
          xyz_y = math.pow(xyz_y, 3)
      else:
          xyz_y = (xyz_y - 16.0 / 116.0) / 7.787
  
      if math.pow(xyz_x, 3) > color_constants.CIE_E:
          xyz_x = math.pow(xyz_x, 3)
      else:
          xyz_x = (xyz_x - 16.0 / 116.0) / 7.787
  
      if math.pow(xyz_z, 3) > color_constants.CIE_E:
          xyz_z = math.pow(xyz_z, 3)
      else:
          xyz_z = (xyz_z - 16.0 / 116.0) / 7.787
  
      xyz_x = (illum["X"] * xyz_x)
      xyz_y = (illum["Y"] * xyz_y)
      xyz_z = (illum["Z"] * xyz_z)
  
      return XYZColor(
          xyz_x, xyz_y, xyz_z, observer=cobj.observer, illuminant=cobj.illuminant)
docs: Convert from Lab to XYZ