docs: def ReadAllClientLabels(self, cursor=None):
      """Reads the user labels for a list of clients."""
  
      cursor.execute("SELECT DISTINCT owner_username, label FROM client_labels")
  
      result = []
      for owner, label in cursor.fetchall():
        result.append(rdf_objects.ClientLabel(name=label, owner=owner))
  
      result.sort(key=lambda label: (label.owner, label.name))
      return result