input: 
  def dict_sum(dictionary):
      """ Computes the sum of values of a given dictionary.
      >>> dict_sum({'A':5, 'B':6, 'C':10})
      21
      """
      sum = 0
      for key, value in dictionary.items():
          sum += value
      return sum
  
output:     sum = 0
      for key, value in dictionary.items():
          sum += value
      return sum