code: def test_pack_unpack():
      x = [[1, 2, 3], [4, 5], [6, 7, 8, 9]]
      n = [len(i) for i in x]
      assert x == _unpack(_pack(x), n)
      return
  
file_path: mystic/mystic/tests/test_dirac_measure.py
imports: from mystic.math.discrete import point_mass
  from mystic.math.discrete import measure
  from mystic.math.discrete import product_measure
  from mystic.math.samples import random_samples
  from mystic.math.grid import samplepts
  from mystic.math import almostEqual
  from mystic.math.measures import *
  from mystic.math.measures import _pack, _unpack
label_desc: Use image node_id 3 for calling a global function with example usage: test_pack_unpack() without return types