Create a linked hash set containing all elements.
Creates a linked hash set as by new LinkedHashSet<E>() and adds each
element of elements to this set in the order they are iterated.
All the elements should be instances of E.
The elements iterable itself may have any element type,
so this constructor can be used to down-cast a Set, for example as:
Set<SuperType> superSet = ...;
Iterable<SuperType> tmp = superSet.where((e) => e is SubType);
Set<SubType> subSet = new LinkedHashSet<SubType>.from(tmp);
factory LinkedHashSet.from(Iterable elements) {
LinkedHashSet<E> result = new LinkedHashSet<E>();
for (final element in elements) {
result.add(element);
}
return result;
}