code: def vpack(boxes, padding=0, strength="strong"):
      """
      Stack LayoutBox instances from top to bottom
      """
  
      for i in range(1, len(boxes)):
          c = boxes[i - 1].bottom - padding >= boxes[i].top
          boxes[i].solver.addConstraint(c | strength)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import itertools
  import kiwisolver
  import logging
  import numpy
  import warnings
  import matplotlib
label_desc: Use image node_id 5 for calling a global function with example usage: vpack(boxes, padding, strength) without return types