made changes to the code by adding headings to the steps

solutions/challenge_9/sum_of_digits.py

@@ -10,6 +10,7 @@
 @author: Semira Tesfai
 """
 
+
 def sum_of_digits(n: int) -> int:
     """Calculate the sum of the digits of a positive integer.
 

solutions/tests/challenge_9/test_sum_of_digits.py

@@ -6,7 +6,8 @@
 """
 
 import unittest
-from sum_of_digits import sum_of_digits
+from solutions.challenge_9.sum_of_digits import sum_of_digits
+
 
 class TestSumOfDigits(unittest.TestCase):
     """Tests for the sum_of_digits function."""
@@ -30,8 +31,8 @@ def test_invalid_input(self):
         with self.assertRaises(AssertionError):
             sum_of_digits(4.5)
         with self.assertRaises(AssertionError):
-            sum_of_digits('123')
+            sum_of_digits("123")
 
-if __name__ == '__main__':
-    unittest.main()
 
+if __name__ == "__main__":
+    unittest.main()