code: public <V> EntryStream<T, V> cross(Collection<? extends V> other) {
          if (other.isEmpty())
              return new EntryStream<>(Spliterators.emptySpliterator(), context);
          return cross(t -> of(other));
      }
docs: Performs a cross product of current stream with specified
  {@link Collection} of elements. As a result the {@link EntryStream} is
  created whose keys are elements of current stream and values are elements
  of the specified collection.
  
  <p>
  The resulting stream contains all the possible combinations of keys and
  values.
  
  <p>
  This is an <a href="package-summary.html#StreamOps">intermediate</a>
  operation.
  
  @param <V> the type of collection elements
  @param other the collection to perform a cross product with
  @return the new {@code EntryStream}
  @throws NullPointerException if other is null
  @since 0.2.3