refactor: narrow the return type of isPOJO
refactor: narrow the return type of isPOJO

ReactiveX/RxJS,benlesh/RxJS,ReactiveX/rxjs,benlesh/RxJS,ReactiveX/rxjs,martinsik/rxjs,benlesh/RxJS,martinsik/rxjs,benlesh/RxJS,martinsik/rxjs,ReactiveX/rxjs,ReactiveX/RxJS,martinsik/rxjs,ReactiveX/RxJS,ReactiveX/rxjs,ReactiveX/RxJS