def pickySum(self, list):
      errs = []
      for i in list:
         if i % 3 == 0:
            errs.append(i)
      if len(errs) > 0:
         raise Exception("http://example.com/error#invalid_numbers",
                         "one or more numbers are multiples of 3", errs)
      return reduce(lambda x, y: x + y, list)