code: public static <T> StreamEx<T> of(Iterator<? extends T> iterator) {
          return of(new UnknownSizeSpliterator.USOfRef<>(iterator));
      }
docs: Returns a sequential, ordered {@link StreamEx} created from given
  {@link Iterator}.
  
  <p>
  This method is roughly equivalent to
  {@code StreamEx.of(Spliterators.spliteratorUnknownSize(iterator, ORDERED))}
  , but may show better performance for parallel processing.
  
  <p>
  Use this method only if you cannot provide better Stream source (like
  {@code Collection} or {@code Spliterator}).
  
  @param <T> the type of iterator elements
  @param iterator an iterator to create the stream from.
  @return the new stream
  @since 0.5.1