Tighten up psf/black and flake8 (#2024)

* Tighten up psf/black and flake8

* Fix some tests

* Fix some E741

* Fix some E741

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

scheduling/first_come_first_served.py

@@ -28,7 +28,7 @@ def calculate_turnaround_times(
 ) -> List[int]:
     """
     This function calculates the turnaround time of some processes.
-        Return: The time difference between the completion time and the 
+        Return: The time difference between the completion time and the
                 arrival time.
                 Practically waiting_time + duration_time
     >>> calculate_turnaround_times([5, 10, 15], [0, 5, 15])