swap method Null safety
Returns a map with the keys and values swapped. If there are duplicate keys the function throws an argument error (So use with containsDuplicateValues()).
Implementation
Map<V, K> swap() {
Map<V, K> newMap = {};
Set<V> duplicateChecker = Set.from(values);
if (duplicateChecker.length < length) {
throw ArgumentError('There are duplicate'
'values in the Maps values $values. Keys need to be unique therefore the swap could\'t happen');
}
forEach((key, value) {
newMap[value] = key;
});
return newMap;
}