input: Write a function to sort an array using the Insertion Sort algorithm. The function should return the sorted array. If the input array is empty, the function should return an empty 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([1, 2, 3, 4, 6, 7, 8]) == [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]
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