These should now work IPython, after activating RabbitMQ broker and PostgreSQL backend
inner_chord1 = chord([multiply.s(2, 3), multiply.s(3, 4)], reducer.s())
inner_chord2 = chord([multiply.s(4, 5), multiply.s(5, 6)], reducer.s())
outer_chord = group(inner_chord1, inner_chord2) | reducer.s()
outer_chord()