import dataclasses

class JunkComparisonException(BaseException):

    def __str__ (self):
        return "Attempting to perform calculations involving junk values."

@dataclasses.dataclass
class Junk:
    represents: str | None = None

    def __str__ (self):
        return '[{}]'.format(self.represents or 'junk')

    def __repr__ (self):
        return self.__str__()

    def __format__ (self, format):
        return self.__str__()

    def __add__ (self, other):
        return self

    def __radd__ (self, other):
        return self

    def __sub__ (self, other):
        return self

    def __rsub__ (self, other):
        return self