stateset is the list of initial states
    gathered_epsilons is a dictionary of (dst: src) epsilon dictionaries

def _add_epsilon_states(self, stateset, gathered_epsilons):
    '''
    stateset is the list of initial states
    gathered_epsilons is a dictionary of (dst: src) epsilon dictionaries
    '''
    for i in list(stateset):
      if i not in gathered_epsilons:
        gathered_epsilons[i] = {}
        q = _otq()
        q.append(i)
        while q:
          s = q.popleft()
          for j in self._transitions.setdefault(s, {}).setdefault(NFA.EPSILON, set()):
            gathered_epsilons[i][j] = s if j not in gathered_epsilons[i] else self.choose(s, j)
            q.append(j)
      stateset.update(gathered_epsilons[i].keys())