associateByTo<K> method
Populates and returns the destination
mutable map with key-value pairs,
where key is provided by the keySelector
function applied to each element of the given collection
and value is the element itself.
If any two elements would have the same key returned by keySelector
the last one gets added to the map.
Implementation
Map<K, T> associateByTo<K>(Map<K, T> destination, K Function(T) keySelector) {
for (var element in this) {
destination[keySelector(element)] = element;
}
return destination;
}