doesn't "elif n is None:" cover that tho?

def arr(n):
x = []
if n == 0:
return []
elif n is None:
return []
else:
for i in range(n):
x.append(i)
return x
'''
Traceback (most recent call last):
File "/workspace/default/src/codewars-test/codewars_test/test_framework.py", line 111, in wrapper
func()
File "tests.py", line 7, in basic_tests
test.assert_equals(arr(), [])
TypeError: arr() missing 1 required positional argument: 'n'

'''
I don't understand the error with my code above.

I still can't figure it out...

What does the following error mean?
Traceback (most recent call last):
File "main.py", line 14, in
test.assert_equals(hello(), "Hello, World!")
TypeError: hello() missing 1 required positional argument: 'name'