input: Write a function to take in a dictionary where keys are strings and values are integers, 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": 2, "y": 4, "z": 6})==12
  assert compute_dict_sum({})==0
  assert compute_dict_sum({"p": -3, "q": 7, "r": 0})==4
output: def compute_dict_sum(d):
      return sum(d.values()) if d else 0