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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_event(self, event):
 """Adds an event to the event file. Args: event: An `Event` protocol buffer. """

        if not isinstance(event, event_pb2.Event):
            raise TypeError("Expected an event_pb2.Event proto, "
                            " but got %s" % type(event))
        self._async_writer.write(event.SerializeToString())