code: boolean isDeadEnd(Set<NFAState<T>> nfaSet)
      {
          for (Set<Transition<NFAState<T>>> set : transitions.values())
          {
              for (Transition<NFAState<T>> t : set)
              {
                  if (!nfaSet.contains(t.getTo()))
                  {
                      return false;
                  }
              }
          }
          return true;
      }
docs: Returns true if this state is not accepting and doesn't have any outbound
  transitions.
  @param nfaSet
  @return