input: Write a function to sort a list of numbers using the Insertion Sort algorithm. The function should take a list of integers as input and return a sorted list. If the input list is empty, the function should return an empty list.
  assert insertionSort([2, 4, 7, 3, 8, 6, 1]) == [1, 2, 3, 4, 6, 7, 8]
  assert insertionSort([9, 8, 7, 6, 5, 4, 3, 2, 1]) == [1, 2, 3, 4, 5, 6, 7, 8, 9]
  assert insertionSort([1, 2, 3, 4, 5]) == [1, 2, 3, 4, 5]
  assert insertionSort([]) == []
  assert insertionSort([5, 4, 3, 2, 1]) == [1, 2, 3, 4, 5]
output: def insertionSort(arr):
      for i in range(1, len(arr)):
          key = arr[i]
          j = i - 1
          while j >= 0 and key < arr[j]:
              arr[j + 1] = arr[j]
              j -= 1
          arr[j + 1] = key
      return arr