input: Write a function to shuffle an array of integers in random order. If the given array is empty, return the empty array.
  assert shuffle([1, 5, 9, 4, 2]) in [[1, 5, 9, 4, 2], [1, 5, 4, 9, 2], [1, 9, 5, 4, 2], [1, 9, 4, 5, 2], [1, 4, 9, 5, 2], [1, 4, 5, 9, 2], [5, 1, 9, 4, 2], [5, 1, 4, 9, 2], [5, 9, 1, 4, 2], [5, 9, 4, 1, 2], [5, 4, 9, 1, 2], [5, 4, 1, 9, 2], [9, 1, 5, 4, 2], [9, 1, 4, 5, 2], [9, 5, 1, 4, 2], [9, 5, 4, 1, 2], [9, 4, 5, 1, 2], [9, 4, 1, 5, 2], [4, 1, 9, 5, 2], [4, 1, 5, 9, 2], [4, 9, 1, 5, 2], [4, 9, 5, 1, 2], [4, 5, 9, 1, 2], [4, 5, 1, 9, 2]]
  assert shuffle([]) == []
output: import random
  
  def shuffle(arr):
      random.shuffle(arr)
      return arr