docs: function diff(req, res) {
    // defined and loaded commands
    var cmds = this.execs
      // map of all standard top-level commands
      , map = Constants.MAP
      // output multi bulk reply list
      , list = []
      , k;
  
    for(k in map) {
      if(!cmds[k]) list.push(k);
    }
  
    res.send(null, list);
  }