docs: 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()