input: Write a python function to calculate the difference between the maximum and minimum values in a dictionary.
  assert calculate_difference({'a': 5, 'b': -2, 'c': 3}) == 7
  assert calculate_difference({'x': 10, 'y': 20, 'z': 30}) == 20
  assert calculate_difference({'key1': -10, 'key2': -20, 'key3': -30}) == 20
output: def calculate_difference(d):
      values = d.values()
      return max(values) - min(values)