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 all its values. If the input dictionary is empty, the function should return 0.
  
  assert dict_sum({'A':5, 'B':6, 'C':10}) == 21
  assert dict_sum({}) == 0
  assert dict_sum({'X':1, 'Y':2, 'Z':3}) == 6
output: def dict_sum(d):
      return sum(d.values()) if d else 0