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>

data_structures/binary_tree/basic_binary_tree.py

@@ -1,4 +1,9 @@
-class Node:  # This is the Class Node with a constructor that contains data variable to type data and left, right pointers.
+class Node:
+    """
+    This is the Class Node with a constructor that contains data variable to type data
+    and left, right pointers.
+    """
+
     def __init__(self, data):
         self.data = data
         self.left = None