code: def get_rpndict_flag(self, rpndict):
          
          flag_set = set([rpn.Rpn.solve_rpn(str(v)) is not None for v in rpndict.values()])
          if len(flag_set) == 1 and flag_set.pop():
              return True
          else:
              return False
docs: calculate flag set, the value is True or False,
              if rpndict value is not None, flag is True, or False
              if set with only one item, i.e. True returns,
              means values of rpndict are all valid float numbers,
              then finally return True, or False