forEach method
- void f(- K,
- V
 
override
    Applies action to each key/value pair of the map.
Calling action must not add or remove keys from the map.
final planetsByMass = <num, String>{0.81: 'Venus', 1: 'Earth',
  0.11: 'Mars', 17.15: 'Neptune'};
planetsByMass.forEach((key, value) {
  print('$key: $value');
  // 0.81: Venus
  // 1: Earth
  // 0.11: Mars
  // 17.15: Neptune
});
Implementation
@override
void forEach(void Function(K, V) f) {
  _base.forEach((key, pair) => f(pair.key, pair.value));
}