code: function keyframe() {
      var m;
      var vals = [];
      var pos = position();
  
      while (m = match(/^((\d+\.\d+|\.\d+|\d+)%?|[a-z]+)\s*/)) {
        vals.push(m[1]);
        match(/^,\s*/);
      }
  
      if (!vals.length) return;
  
      return pos({
        type: 'keyframe',
        values: vals,
        declarations: declarations()
      });
    }
docs: Parse keyframe.