code: function(frame) {
      var strCss = '';
      if (frame.type === 'keyframe') {
        strCss += frame.values.join(',') + ' {';
        frame.declarations.forEach(function(declaration) {
          strCss += commentOrDeclaration(declaration);
        });
        strCss += '\n}\n\n';
      } else if (frame.type === 'comment') {
        strCss += processComment(frame) + '\n\n';
      }
      return strCss;
    }
docs: Check keyframe type