python insertion sort algorithm

insertion_sort.py

def insertion_sort(arr: []):

        # Traverse through 1 to len(arr)
    for i in range(1, len(arr)):

        key = arr[i]
        
        # Move elements of arr[0..i-1], that are
        # greater than key, to one position ahead
        # of their current position
        j = i-1
        while j >= 0 and key < arr[j]:
            arr[j + 1] = arr[j]
            j -= 1
        arr[j + 1] = key