Given a set of state and a transitions, the procedure return all states
which can lead in maximum k number of steps to given states, excluding
the given states themselves (in some cases this might be more efficient
the kPred, and then conjuncting out the negation).
Given a set of state and a transitions, the procedure return all states
which can be reached in maximum k number of steps from these states,
excluding the given states themselves (in some cases this might be more
efficient the allSucc, and then conjuncting out the negation).