code: def surround_parse(self, node, pre_char, post_char):
          
          self.add_text(pre_char)
          self.subnode_parse(node)
          self.add_text(post_char)
docs: Parse the subnodes of a given node. Subnodes with tags in the
          `ignore` list are ignored. Prepend `pre_char` and append `post_char` to
          the output in self.pieces.