def get(self, ns, label=None):
        """Return :class:`tags instances<~Tag>` for the namespace `ns`, ordered
        by label.

        If `label` is not None the only one instance may be returned, or
        `None` if no tags exists for this label.
        """
        query = Tag.query.filter(Tag.ns == ns)

        if label is not None:
            return query.filter(Tag.label == label).first()

        return query.all()
Return :class:`tags instances<~Tag>` for the namespace `ns`, ordered
        by label.

        If `label` is not None the only one instance may be returned, or
        `None` if no tags exists for this label.