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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 _delete_collection(self, ctx):
 """ Delete a collection from DB, optionally filtered by ``filter_by`` """

        assert isinstance(ctx, ResourceQueryContext)

        filter_by = ctx.get_filter_by()
        q = self._orm.query(self.model_cls)

        if filter_by is not None:
            q = self.to_filter(q, filter_by)

        return q.delete()