Reading the error suggests that when reading the tests.py file, at ln 2, there's a function call for a function named reverse_seq but there's no function defined in the solution.py file. In other words, the tests are trying to use a function called reverse_seq but there's no function in your proposed solution that has that name.

Make sure the name of your function matches the name of the function that's being used in the test cases.

The second sample test for the python version of this problem has (I believe) a typo. The test expects 219 when the real answer is 129. Double check me on this, as I can't seem to get my code to pass the random tests...

That's a way more elegant method of checking the characters than I did - thanks for teaching me something new!

primes.length = 5133

edit: unfortunately, 5133 isn't a prime number, otherwise I definitely would upvote this solution.