code: def process_event(self, event):
          
          if not isinstance(event, KindleEvent):
              pass
          elif isinstance(event, AddEvent):
              self._data[event.asin] = BookSnapshot(event.asin)
          elif isinstance(event, SetReadingEvent):
              self._data[event.asin].status = ReadingStatus.CURRENT
              self._data[event.asin].progress = event.initial_progress
          elif isinstance(event, ReadEvent):
              self._data[event.asin].progress += event.progress
          elif isinstance(event, SetFinishedEvent):
              self._data[event.asin].status = ReadingStatus.COMPLETED
          else:
              raise TypeError
docs: Apply an event to the snapshot instance