input: Write a function to take a dictionary (string → integer) as input and return 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": 3, "y": 7})==10
  assert compute_dict_sum({"m": 0, "n": 0})==0
  assert compute_dict_sum({})==0
output: def compute_dict_sum(d):
      return sum(d.values())