code: function selectTags(tags) {
    // select all tags
    if (!tags) {
      var keys = Object.keys(__TAG_IMPL);
      return keys + selectTags(keys)
    }
  
    return tags
      .filter(function (t) { return !/[^-\w]/.test(t); })
      .reduce(function (list, t) {
        var name = t.trim().toLowerCase();
        return list + ",[" + IS_DIRECTIVE + "=\"" + name + "\"]"
      }, '')
  }
docs: Get selectors for tags
  @param   { Array } tags - tag names to select
  @returns { String } selector