Update MergeSort.py (#927)

Remove the self parameter from both the merge() and mergeSort() functions as they are not instance methods of the class.
Rename the arr parameter in the mergeSort() function to unsorted_list or something similar to make it more descriptive.
Add type hints to the function parameters and return values to improve code readability and maintainability.
Update the docstring of the mergeSort() function to adhere to the Python docstring conventions.                                                                                                                                                                                                                                     Note: I assumed that the input list contains only integers. If the list can contain any type of elements, you may need to modify the code accordingly.

Signed-off-by: NIKITA PANDEY <113332472+nikitapandeyy@users.noreply.github.com>

Author: nikitapandeyy

Python/Algorithms/DivideAndConquer/MergeSort.py

@@ -1,4 +1,16 @@
-def merge(self, left, right):
+from typing import List
+
+
+def merge(left: List[int], right: List[int]) -> List[int]:
+    """Merges two sorted lists into a single sorted list.
+
+    Args:
+        left (list): The left half of the list to be merged.
+        right (list): The right half of the list to be merged.
+
+    Returns:
+        list: The sorted list resulting from merging the left and right halves.
+    """
     if len(left) == 0:
         return right
 
@@ -26,23 +38,20 @@ def merge(self, left, right):
     return result
 
 
-def mergeSort(self, arr):
-    """ mergeSort Algorithm Implementation in Python 3
+def merge_sort(unsorted_list: List[int]) -> List[int]:
+    """Sorts a list of integers using the merge sort algorithm.
 
-        arr : Unorded list
-        output : Return list in ascending order.
-        time complexity : O(n log2n)
-        Note : O(n log2n) is the best possible worst-case runtime that can be
-        achieved by a sorting algorithm.
+    Args:
+        unsorted_list (list): The unsorted list to be sorted.
 
-        Example :
-        >>> mergeSort([4,2,6,5,9,8])
-        [2, 4, 5, 6, 8, 9]"""
+    Returns:
+        list: The sorted list.
+    """
+    if len(unsorted_list) < 2:
+        return unsorted_list
 
-    if len(arr) < 2:
-        return arr
+    midpoint = len(unsorted_list) // 2
 
-    midpoint = len(arr) // 2
+    return merge(left=merge_sort(unsorted_list[:midpoint]),
+                 right=merge_sort(unsorted_list[midpoint:]))
 
-    return merge(left=mergeSort(arr[:midpoint]),
-                 right=mergeSort(arr[midpoint:]))