input: def dict_sum(dict):
      sum = 0
      for key, value in dict.items():
          sum += value
      return sum
  
  """
  >>> dict_sum({'A':5, 'B':6, 'C':10})
  21
  >>> dict_sum({'X':1, 'Y':2, 'Z':3})
  6
  >>> dict_sum({})
  0
  """
output:     sum = 0
      for key, value in dict.items():
          sum += value
      return sum