code: def unsign(self, value, max_age=None):
          
          result = super(TimestampSigner, self).unsign(value)
          value, timestamp = result.rsplit(self.sep, 1)
          timestamp = baseconv.base62.decode(timestamp)
          if max_age is not None:
              if isinstance(max_age, datetime.timedelta):
                  max_age = max_age.total_seconds()
              # Check timestamp is not older than max_age
              age = time.time() - timestamp
              if age > max_age:
                  raise SignatureExpired(
                      'Signature age %s > %s seconds' % (age, max_age))
          return value
docs: Retrieve original value and check it wasn't signed more
          than max_age seconds ago.