max method
Returns the maximum value in iterable, according to the order specified by the
compare function, or null if iterable is empty.
The compare function must act as a Comparator. If compare is omitted,
Comparable.compare is used. If iterable contains null elements, an exception
will be thrown.
Implementation
E? max([Comparator<E>? compare]) {
if (isEmpty) return null;
final compare0 = compare ?? _compareAny;
return reduce((a, b) => compare0(a, b) > 0 ? a : b);
}