input: Write a python function to make a copy of an array.
  assert copy_array([1, 2, 3, 4, 5]) == [1, 2, 3, 4, 5]
  assert copy_array([10, 20, 30, 40, 50]) == [10, 20, 30, 40, 50]
  assert copy_array([]) == []
  assert copy_array([1]) == [1]
output: def copy_array(arr):
      return arr[:]