code: def _remove_whitespace_nodes(self, node, unlink=True):
          
          remove_list = []
          for child in node.childNodes:
              if child.nodeType == Node.TEXT_NODE and not child.data.strip():
                  remove_list.append(child)
              elif child.hasChildNodes():
                  self._remove_whitespace_nodes(child, unlink)
          for node in remove_list:
              node.parentNode.removeChild(node)
              if unlink:
                  node.unlink()
docs: 删除空白无用节点