input: Write a python function to double the values of the items in a dictionary.
  assert double_values({'chair': 4, 'table': 2, 'sofa': 5}) == {'chair': 8, 'table': 4, 'sofa': 10}
  assert double_values({'pen': 1, 'pencil': 3, 'eraser': 2}) == {'pen': 2, 'pencil': 6, 'eraser': 4}
  assert double_values({'apple': 10, 'banana': 5}) == {'apple': 20, 'banana': 10}
output: def double_values(d):
      return {k: v * 2 for k, v in d.items()}