input: Write a function to compute the sum of the values of a given dictionary.
  def dict_sum(dictionary):
      sum = 0
      for key, value in dictionary.items():
          sum += value
      return sum
  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(dictionary):
      sum = 0
      for key, value in dictionary.items():
          sum += value
      return sum