input: Write a function to swap the elements of two input arrays of integers. Ensure that the two arrays are of the same length before performing the swap. Return the modified arrays as a tuple.
  assert swap([3, 5, 6, 9], [2, 4, 7, 8])==([2, 4, 7, 8], [3, 5, 6, 9])
  assert swap([1, 2], [3, 4])==([3, 4], [1, 2])
  assert swap([10], [20])==([20], [10])
  assert swap([5, 5, 5], [6, 6, 6])==([6, 6, 6], [5, 5, 5])
  assert swap([], [])==([], [])
output: def swap(arr1, arr2):
      if len(arr1) != len(arr2):
          return None
      for i in range(len(arr1)):
          arr1[i], arr2[i] = arr2[i], arr1[i]
      return (arr1, arr2)