none method
Whether no element satisfies test.
Returns true if no element satisfies test,
and false if at least one does.
Equivalent to iterable.every((x) => !test(x)) or
!iterable.any(test).
Implementation
bool none(bool Function(T) test) {
  for (var element in this) {
    if (test(element)) return false;
  }
  return true;
}