input: Write a function to compute the sum of all values in a dictionary where the keys are strings and the values are integers. If the dictionary is empty, return 0.
  assert compute_dict_sum({'a': 5, 'b': 10, 'c': 15})==30
  assert compute_dict_sum({'x': -1, 'y': 2, 'z': -3})==-2
  assert compute_dict_sum({})==0
  assert compute_dict_sum({'apple': 4, 'banana': 7})==11
output: def compute_dict_sum(d):
      return sum(d.values()) if d else 0