def test_equals_2(self):
     self.assertEqual(filter_string("a1b2c3"), 123)
 def test_equals(self):
     self.assertEqual(filter_string("123"), 123)
 def test_equals_4(self):
     self.assertEqual(filter_string("aa 112 3dd"), 1123)
 def test_equals_5(self):
     self.assertEqual(filter_string("11bb2c23c3"), 112233)
 def test_equals_3(self):
     self.assertEqual(filter_string("aa1bb2cc3dd"), 123)