func Singlep(iter Enumerable, pred Predicate) (retval interface{}, err error) {
	iter = Where(iter, pred)
	return Single(iter)
}
func Singlep(iter Enumerable, pred Predicate) (retval interface{}, err error) {
	iter = Where(iter, pred)
	return Single(iter)
}
func Singlep ( iter Enumerable , pred Predicate ) ( retval interface { } , err error ) { iter = Where ( iter , pred ) return Single ( iter ) }
// Singlep retrieces the only element from a list that matches a criteria. If
// no match is found, or two or more are found, `Singlep` returns nil and an
// error.
Singlep retrieces the only element from a list that matches a criteria . If no match is found or two or more are found Singlep returns nil and an error .