code: public static <E> ImmutableMultiset<E> copyOf(Iterator<? extends E> elements) {
      return new ImmutableMultiset.Builder<E>().addAll(elements).build();
    }
docs: Returns an immutable multiset containing the given elements, in the "grouped iteration order"
  described in the class documentation.
  
  @throws NullPointerException if any of {@code elements} is null