code: def get(self, key, dt):
          
          try:
              return self._cache[key].unwrap(dt)
          except Expired:
              self.cleanup(self._cache[key]._unsafe_get_value())
              del self._cache[key]
              raise KeyError(key)
docs: Get the value of a cached object.
  
          Parameters
          ----------
          key : any
              The key to lookup.
          dt : datetime
              The time of the lookup.
  
          Returns
          -------
          result : any
              The value for ``key``.
  
          Raises
          ------
          KeyError
              Raised if the key is not in the cache or the value for the key
              has expired.