input: Write a function to take two arrays of integers and swap their elements. The function should ensure that both arrays have the same length before swapping. After the swap, the elements in the first array should be from the second array and vice versa.
  
  def swap_arrays(arr1, arr2):
      assert len(arr1) == len(arr2)
      for i in range(len(arr1)):
          temp = arr1[i]
          arr1[i] = arr2[i]
          arr2[i] = temp
  
  assert swap_arrays([3, 5, 6, 9], [2, 4, 7, 8])==None
  assert swap_arrays([1, 2, 3], [4, 5, 6])==None
  assert swap_arrays([10, 20], [30, 40])==None
  assert swap_arrays([1, 2, 3, 4], [5, 6, 7, 8])==None
  assert swap_arrays([9, 8, 7], [6, 5, 4])==None
  assert swap_arrays([], [])==None
output: def swap_arrays(arr1, arr2):
      if len(arr1) == len(arr2):
          for i in range(len(arr1)):
              arr1[i], arr2[i] = arr2[i], arr1[i]