code: function(n) {
      var type = this.lookahead(n).type;
      if ('=' == type && this.bracketed) return true;
      return ('ident' == type || 'string' == type)
        && ']' == this.lookahead(n + 1).type
        && ('newline' == this.lookahead(n + 2).type || this.isSelectorToken(n + 2))
        && !this.lineContains(':')
        && !this.lineContains('=');
    }
docs: Check if the following sequence of tokens
  forms an attribute selector.