The snippet that filters the filtered set is

Question

Admin · Accepted Answer

var t=new FilteredSet(s, {function(s) {return !(x instanceof Set);});

Admin · Answer

var t=new FilteredSet{function(s) {return !(x instanceof Set);});

Admin · Answer

var t=new FilteredSet(s, {function(s) {return (x instanceof Set);});

Admin · Answer

var t=new FilteredSet(s, {function(s) {return x;});

Q. The snippet that filters the filtered set is