input: Write a function to sum the values of a dictionary.
  assert sum_values({"a": 10, "b": 20, "c": 30}) == 60
  assert sum_values({"x": 5, "y": 15, "z": 25}) == 45
  assert sum_values({"key1": 100, "key2": 200, "key3": 300}) == 600
output: def sum_values(d):
      return sum(d.values())