code: function(mythis) {
      // finalize any blocks not matched
      while (!already_done && oldtip != last_matched_container) {
        mythis.finalize(oldtip, line_number);
        oldtip = oldtip.parent;
      }
      var already_done = true;
    }
docs: This function is used to finalize and close any unmatched blocks.  We aren't ready to do this now, because we might have a lazy paragraph continuation, in which case we don't want to close unmatched blocks.  So we store this closure for use later, when we have more information.