code: function (){
      if (!instance._once) return;
      
      //Uncache the files
      ["index.js", "command.js", "argp.js", "body.js", "error.js", "wrap.js"]
      .forEach (function (filename){
        delete require.cache[__dirname + path.sep + filename];
      });
      
      //The user may have a reference to the instance so it should be freed, eg.
      //var p = argp.createParser (). If the user doesn't free the instance, eg.
      //p = null, it will retain an empty object, {}
      for (var p in instance){
        delete instance[p];
      }
      instance.__proto__ = null;
      delete instance.constructor;
    }
docs: The Argp and Command instances execute this code