input: Write a function to sort an array of integers using the Insertion Sort algorithm. If the array is empty, return the empty array. The function should return the sorted array.
  
  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([]) == []
  assert insertionSort([5, 3, 8, 4, 6]) == [3, 4, 5, 6, 8]
  assert insertionSort([9, 1, 5, 4, 8, 0]) == [0, 1, 4, 5, 8, 9]
  assert insertionSort([3, 2, 1]) == [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