keys property
override
The keys of this Map.
The returned iterable has efficient length and contains operations,
based on length and containsKey of the map.
The order of iteration is defined by the individual Map implementation,
but must be consistent between changes to the map.
Modifying the map while iterating the keys may break the iteration.
Implementation
@override
Iterable<K> get keys => _base.values.map((pair) => pair.key);