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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:
 async def clear(self, using_db=None) -> None: """ Clears ALL relations. """

        db = using_db if using_db else self.model._meta.db
        through_table = Table(self.field.through)
        query = (
            db.query_class.from_(through_table)
            .where(getattr(through_table, self.field.backward_key) == self.instance.id)
            .delete()
        )
        await db.execute_query(str(query))