Returns a list of Tasks leased for a certain time.

    Args:
      queue: The queue to query from.
      lease_seconds: The tasks will be leased for this long.
      limit: Number of values to fetch.

    Returns:
        A list of GrrMessage() objects leased.

def QueryAndOwn(self, queue, lease_seconds=10, limit=1):
    """Returns a list of Tasks leased for a certain time.

    Args:
      queue: The queue to query from.
      lease_seconds: The tasks will be leased for this long.
      limit: Number of values to fetch.

    Returns:
        A list of GrrMessage() objects leased.
    """
    with self.data_store.GetMutationPool() as mutation_pool:
      return mutation_pool.QueueQueryAndOwn(queue, lease_seconds, limit,
                                            self.frozen_timestamp)