util files moved form kern to util package

kern/iterator.go

@@ -45,3 +45,8 @@ type ExtIterator interface {
 func ErrNoOperation(name string) error {
 	return fmt.Errorf("no %s() function defined in the data-source", name)
 }
+
+func IsIterator(v any) (ok bool) {
+	_, ok = v.(Iterator)
+	return
+}