input: Write a function to clear all keys in a dictionary.
  assert clear_dictionary({'a': 1, 'b': 2, 'c': 3}) == {}
  assert clear_dictionary({1: 'one', 2: 'two'}) == {}
  assert clear_dictionary({'x': 10, 'y': 20, 'z': 30}) == {}
output: def clear_dictionary(d):
      d.clear()
      return d