input: Write a function to compute the sum of the values in a given dictionary. The function should take a dictionary as input and return the sum of its values. If the dictionary is empty, the function should return 0.
  assert dict_sum({'A': 5, 'B': 6, 'C': 10}) == 21
  assert dict_sum({}) == 0
output: def dict_sum(d):
      return sum(d.values()) if d else 0