src/main/java/org/organicdesign/fp/collections/PersistentHashSet.java
public static <E> PersistentHashSet<E> of(Iterable<E> elements) {
        PersistentHashSet<E> empty = empty();
        MutableSet<E> ret = empty.mutable();
        for (E e : elements) {
            ret.put(e);
        }
        return (PersistentHashSet<E>) ret.immutable();
    }
public static <E> PersistentHashSet<E> of(Iterable<E> elements) {
        PersistentHashSet<E> empty = empty();
        MutableSet<E> ret = empty.mutable();
        for (E e : elements) {
            ret.put(e);
        }
        return (PersistentHashSet<E>) ret.immutable();
    }
Returns a new PersistentHashSet of the values.  The vararg version of this method is
{@link org.organicdesign.fp.StaticImports#set(Object...)}   If the input contains duplicate
elements, later values overwrite earlier ones.

@param elements The items to put into a vector.
@return a new PersistentHashSet of the given elements.