def test_true_2(self):
     self.assertTrue(valid_parentheses("hi(hi)()"))
 def test_false_3(self):
     self.assertFalse(valid_parentheses("hi())("))
 def test_true_1(self):
     self.assertTrue(valid_parentheses(""))
 def test_false_2(self):
     self.assertFalse(valid_parentheses(")test"))