code: public static <E> RubyEnumerator<E> copyOf(Iterable<E> iter) {
      Objects.requireNonNull(iter);
  
      return new RubyEnumerator<>(RubyArray.copyOf(iter));
    }
docs: Returns a {@link RubyEnumerator} which copies the elements of given
  Iterable.
  
  @param iter
  any Iterable
  @return {@link RubyEnumerator}
  @throws NullPointerException
  if iter is null