firstOrDefault method

Implementation

E? firstOrDefault([bool Function(E element)? test]) {
  if (test == null) {
    Iterator<E> it = iterator;
    if (!it.moveNext()) {
      return null;
    }
    return it.current;
  }
  for (E element in this) {
    if (test(element)) return element;
  }
  return null;
}