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.
  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())