code: public Set<NFAState<T>> epsilonClosure(Scope<DFAState<T>> scope)
      {
          Set<NFAState<T>> set = new HashSet<>();
          set.add(this);
          return epsilonClosure(scope, set);
      }
docs: Creates a dfa state from all nfa states that can be reached from this state
  with epsilon move.
  @param scope
  @return