input: Write a python function to find the difference between the maximum and minimum values in an array.
  assert get_difference([100, 45, 56, 30, 90, 100]) == 70
  assert get_difference([10, 20, 30, 40, 50]) == 40
  assert get_difference([1, 1, 1, 1, 1]) == 0
output: def get_difference(arr):
      return max(arr) - min(arr)