<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def truncate(self, async_=False, **kw):
 """ truncate this table. :param async_: run asynchronously if True :return: None """

        from .tasks import SQLTask
        async_ = kw.get('async', async_)
        task = SQLTask(name='SQLTruncateTableTask', query='truncate table %s.%s' % (self.project.name, self.name))
        instance = self.project.parent[self._client.project].instances.create(task=task)

        if not async_:
            instance.wait_for_success()
        else:
            return instance