add: if(res instanceof MochiKit.Async.Deferred){ throw new Error("Deferred instances can only be chained if they are the result of a callback"); } 
context: },callback:function(res){this._check();this._resback(res);},errback:function(res){
meta: 8607	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/8607/8b42fb2ed090da7f1e336726dcb69d2649658e7c/MochiKit.js/clean/trunk/lib/MochiKit.js