input: Write a function to sort a list of numbers using the Insertion Sort algorithm. If the given list is empty, return the list as it is.
  assert insertionSort([3, 4, 5, 1, 2])==[1, 2, 3, 4, 5]
  assert insertionSort([3, 5, 10, 1, 2])==[1, 2, 3, 5, 10]
  assert insertionSort([4, 3, 1, 2])==[1, 2, 3, 4]
  assert insertionSort([3, 5, 4, 1, 2])==[1, 2, 3, 4, 5]
  assert insertionSort([])==[]
output: def insertionSort(arr):
      if not arr:
          return 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