code: def sort_nodes(dom, cmp_func):
      dom.normalize()
      for node in list(walk_dom(dom, elements_only=True)):
          prev_sib = node.previousSibling
          while prev_sib and cmp_func(prev_sib, node) == 1:
              node.parentNode.insertBefore(node, prev_sib)
              prev_sib = node.previousSibling