input: Write a function that takes in a dictionary (with string keys and integer values) and returns the sum of all values in the dictionary. If the dictionary is empty, return 0.
  assert compute_dict_sum({"a": 5, "b": 10, "c": 15})==30
  assert compute_dict_sum({"x": 2, "y": 4, "z": 6})==12
  assert compute_dict_sum({})==0
output: def compute_dict_sum(d):
      return sum(d.values()) if d else 0