 (content instanceof Array) {
        for (var i = 0, n = content.length; i < n; ++i) {
          var tag = content[i];
          if (tag === openTag || tag === excludedTag) { continue; }
          return tag;
        }
        return null;
      } else {
        return content;
      }
    }

    function makeHtmlString(openTag, closeTag) {
      if (openTag === closeTag) { return null; }
      var stack = containmentStackFor(openTag, [closeTag]);
      if (stack == null) { return null; }
      if (closeTa