The keys of thisMap.

The returned iterable has efficientlength andcontains operations,based onlength andcontainsKey of the map.

The order of iteration is defined by the individualMap implementation,but must be consistent between changes to the map.

Modifying the map while iterating the keys may break the iteration.

Implementation

Iterable<String> get keys {  final keys = <String>[];  forEach((k, v) => keys.add(k));  return keys;}