Pyupgrade to Python 3.9 (#4718)

* Pyupgrade to Python 3.9

* updating DIRECTORY.md

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

sorts/bitonic_sort.py

@@ -3,10 +3,10 @@ Python program for Bitonic Sort.
 
 Note that this program works only when size of input is a power of 2.
 """
-from typing import List
+from __future__ import annotations
 
 
-def comp_and_swap(array: List[int], index1: int, index2: int, direction: int) -> None:
+def comp_and_swap(array: list[int], index1: int, index2: int, direction: int) -> None:
     """Compare the value at given index1 and index2 of the array and swap them as per
     the given direction.
 
@@ -37,7 +37,7 @@ def comp_and_swap(array: List[int], index1: int, index2: int, direction: int) ->
         array[index1], array[index2] = array[index2], array[index1]
 
 
-def bitonic_merge(array: List[int], low: int, length: int, direction: int) -> None:
+def bitonic_merge(array: list[int], low: int, length: int, direction: int) -> None:
     """
     It recursively sorts a bitonic sequence in ascending order, if direction = 1, and in
     descending if direction = 0.
@@ -61,7 +61,7 @@ def bitonic_merge(array: List[int], low: int, length: int, direction: int) -> No
         bitonic_merge(array, low + middle, middle, direction)
 
 
-def bitonic_sort(array: List[int], low: int, length: int, direction: int) -> None:
+def bitonic_sort(array: list[int], low: int, length: int, direction: int) -> None:
     """
     This function first produces a bitonic sequence by recursively sorting its two
     halves in opposite sorting orders, and then calls bitonic_merge to make them in the