code: def AddClientLabels(self, client_id, owner, labels, cursor=None):
      
      cid = db_utils.ClientIDToInt(client_id)
      labels = set(labels)
      args = [(cid, mysql_utils.Hash(owner), owner, label) for label in labels]
      args = list(collection.Flatten(args))
  
      query = """
            INSERT IGNORE INTO client_labels
                (client_id, owner_username_hash, owner_username, label)
            VALUES {}
            """.format(", ".join(["(%s, %s, %s, %s)"] * len(labels)))
      try:
        cursor.execute(query, args)
      except MySQLdb.IntegrityError as e:
        raise db.UnknownClientError(client_id, cause=e)
docs: Attaches a list of user labels to a client.