input: Write a function to take as input two arrays of integers and swap their elements.
  assert swap([3, 5, 6, 9], [2, 4, 7, 8])==None
  assert swap([1, 2], [3, 4])==None
  assert swap([1], [2])==None
  assert swap([5, 7], [7, 5])==None
  assert swap([8, 9], [9, 8])==None
output: def swap(arr1, arr2):
      arr1[:], arr2[:] = arr2[:], arr1[:]