code: function() {
      var i = 2
        , type;
      switch (this.lookahead(i).type) {
        case '{':
        case 'indent':
        case ',':
          return true;
        case 'newline':
          while ('unit' == this.lookahead(++i).type
              || 'newline' == this.lookahead(i).type) ;
          type = this.lookahead(i).type;
          return 'indent' == type || '{' == type;
      }
    }
docs: Check if the following sequence of tokens
  forms a keyframe block.