code: def update_rpndict(self, rpndict):
          
          tmpdict = {k: v for k, v in rpndict.items()}
          for k, v in rpndict.items():
              v_str = str(v)
              if rpn.Rpn.solve_rpn(v_str) is None:
                  tmpdict[k] = self.rinse_rpnexp(v_str, tmpdict)
              else:
                  tmpdict[k] = rpn.Rpn.solve_rpn(v_str)
          return tmpdict
docs: update rpndict, try to solve rpn expressions as many as possible,
              leave unsolvable unchanged.
  
              return new dict