def MAY!(m)
      RequirementLevel::Low.new(m, false, subject, *challenges).result(true)
    end
def MAY!(m)
      RequirementLevel::Low.new(m, false, subject, *challenges).result(true)
    end
@example _Optional_ definition with isolation
   it { 'foo'.bar }.MAY! match /^foo$/

 @see MAY