The first is a string, the second an int.
You can't accept int's

Having the same problem , have you figured it out whats the problem here

The bugs with the random tests when using Python, described below, still seem to be present.

Your toString() method should be called:

def __str__(self)

See https://docs.python.org/2/reference/datamodel.html#object.__str__

When I Run Tests they all pass, but when I try to Submit I fail on the 10th test.

Priting out the test MongoIDs and the function being called gives:

is_valid:
s = 333333333333333333333333
Test Passed
is_valid:
s = 333333333333333333333333
True should equal False

So the 9th test seems to be identical to the 10th test, but one passes and the other doesn't.

Am I missing something?