input: Write a python function to reverse the elements of an array.
  assert reverse([1, 2, 3, 4, 5]) == [5, 4, 3, 2, 1]
  assert reverse(['a', 'b', 'c']) == ['c', 'b', 'a']
  assert reverse([True, False, True]) == [True, False, True]
  assert reverse([]) == []
output: def reverse(arr):
      return arr[::-1]