docs: function zrange(start, end, withscores) {
    var i
      , len = this._keys.length
      , list = [];
    if(start < 0) start = len + start;
    if(end < 0) end = len + end;
    if(start < 0) start = 0;
    if(end >= len) end = len - 1;
    i = start;
    for(;i <= end;i++) {
      list.push(this._keys[i].m);
      if(withscores) list.push(this._keys[i].v);
    }
    return list;
  }