• Test suite structure is wrong
• Trivial arithmetic is not a novel kata idea

approx_equals should be used instead of assert_equals due to possibilities of rounding errors

The input validation is worthless and should be removed

You should try to Rephrase the description, its kinda confusing

na_true_false(3, 4) => False (because 3 = True, and -4 = False)

Probably here is missprint and it should be

na_true_false(3, -4)

• Task description should come before examples
• Input validation is a worthless requirement and should be removed
• The user's solution and test framework should be imported explicitly
• Sample tests are not correctly structured
• Final tests are not correctly structured
• Comparing values is not a novel kata idea

IMO if any of the arguments are None then the return value should be False rather than None.

Do these two sides form a right triangle? False.

• Python new test framework should be used in sample test part with it inside describe block (here's some info)

• Parameter name should be snake_case as well

No random tests. You should read this documentation on the topic.

Python naming convention requires snake_case for the function name.