def METHOD_NAME(out, problem, variables, extend=False):
    """This hook is normally used for post-processing (additional results can
    be inserted into `out` dictionary), but here we just verify the weak
    incompressibility condition."""
    from sfepy.base.base import nm, output, assert_
    one = nm.ones((variables['p'].field.n_nod,), dtype=nm.float64)
    variables.set_state_parts({'p' : one})
    zero = problem.evaluate('dw_stokes.i1.Omega(u, p)')
    output('div(u) = %.3e' % zero)
    assert_(abs(zero) < 1e-14)
    return out