code: def query(self, ns, selector='*'):
      
      q, r = HicaLabelStore.PREFIX + '.' + ns, []
      for (key, value) in self.items:
        if not selector and key == q:
          r.append((key, value))
        if key.startswith(q) and key != q:
          sub = key[len(q):]
          m = re.match('.' + selector, sub)
          if m:
            r.append((key, value))
      return r
docs: Query the label store for labels
  
      :param ns: Label namespace (`bind_pwd` for example)
      :type ns: str
      :param selector: Target selector (`test` or `test.guest` for example)
      :type selector: str