code: def unwrap(self, dt):
          
          expires = self._expires
          if expires is AlwaysExpired or expires < dt:
              raise Expired(self._expires)
          return self._value
docs: Get the cached value.
  
          Returns
          -------
          value : object
              The cached value.
  
          Raises
          ------
          Expired
              Raised when `dt` is greater than self.expires.