input: Write a function that takes in a dictionary (string → integer) and returns the sum of all values in the dictionary.
  
  assert compute_dict_sum({"a": 5, "b": 10, "c": 15})==30
  assert compute_dict_sum({"x": 1, "y": 2, "z": 3})==6
  assert compute_dict_sum({})==0
output: def compute_dict_sum(d):
      return sum(d.values())