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