forEach method
Applies action
to each key-value pair of the map in order of MRU to
LRU.
Calling action
must not add or remove keys from the map.
Implementation
@override
void forEach(void Function(K key, V value) action) {
var tail = _tail;
while (tail != null) {
action(tail.key, tail.value);
tail = tail.previous;
}
}