code: public Collection<E> internAll(@NonNull Iterable<? extends E> iterable) {
        return asStream(iterable).map(this::intern).collect(Collectors.toList());
     }
docs: <p>Interns all elements in the given iterable.</p>
  
  @param iterable the items of elements to intern.
  @return the interned elements.
  @throws NullPointerException if the collection is null