def test_Empty(self):
   emp = NFA.build_empty()
   self.assert_(emp.initial)
   self.assert_(emp.finals)
   self.assertEqual(len(emp.states) , 2)
   self.assertEqual(
     emp.states[emp.initial],
     dict({'': emp.finals})
   )
 def result(self):
   if len(self._result) == 1:
     return self._result[0]
   elif len(self._result) == 0:
     return NFA.build_empty()
   else:
     print 'got multiple nfas?!'
     for n in self._result:
       print n, n.states
     assert False