code: def _expire_item(self, key):
          
          (timeout, callback) = self._timeouts[key]
          now = time.time()
          if timeout <= now:
              item = dict.pop(self, key)
              del self._timeouts[key]
              if callback:
                  try:
                      callback(key, item)
                  except TypeError:
                      try:
                          callback(key)
                      except TypeError:
                          callback()
              return None
          else:
              return timeout - now
docs: Do the expiration of a dictionary item.
  
          Remove the item if it has expired by now.
  
          :Parameters:
              - `key`: key to the object.
          :Types:
              - `key`: any hashable value