input: Write a function to sort a given array in ascending order using the bubble sort algorithm. The function should modify the array in place.
  
  def bubble_sort(arr): 
      n = len(arr) 
      for i in range(n-1):
          for j in range(0, n-i-1): 
              if arr[j] > arr[j+1] : 
                  arr[j], arr[j+1] = arr[j+1], arr[j] 
  
  assert bubble_sort([3, 7, 4, 1])==[1, 3, 4, 7]
  assert bubble_sort([5, 2, 9, 1, 5, 6])==[1, 2, 5, 5, 6, 9]
  assert bubble_sort([10, 8, 6, 4, 2, 0])==[0, 2, 4, 6, 8, 10]
  assert bubble_sort([])==[]
  assert bubble_sort([1])==[1]
output: def bubble_sort(arr): 
      n = len(arr) 
      for i in range(n-1):
          for j in range(0, n-i-1): 
              if arr[j] > arr[j+1] : 
                  arr[j], arr[j+1] = arr[j+1], arr[j]