input: Write a function to compute the sum of the values of 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({'X': 1, 'Y': 2, 'Z': 3})==6
  assert dict_sum({})==0
output: def dict_sum(d):
      return sum(d.values()) if d else 0