input: Write a function to take an array of integer values and reverse the order of the values.
  assert reverse_array([1, 2, 3, 4, 5])==[5, 4, 3, 2, 1]
  assert reverse_array([7, 8, 9, 10])==[10, 9, 8, 7]
  assert reverse_array([2, 4, 6, 8, 10])==[10, 8, 6, 4, 2]
output: def reverse_array(arr):
      return arr[::-1]