[dune-pdelab] How to impose pure Neumann boundary condition

[Jizhou Li]

Hi,
I am very new to dune-pdelab. On the pdelab-howto-article page 132-133, it says dune-pdelab can handle pure Neumann boundary condition. Does anyone know how to get it done? Or just to construct finite element space with {q:  ∫q dΩ=0}. I think it would be helpful for to have an example on howto-article for beginners.

Thanks

Jizhou Li