def has_writes(tw_vectors):
    """
    :param tw_vectors: See
        ``allmydata.interfaces.TestAndWriteVectorsForShares``.

    :return bool: ``True`` if any only if there are writes in ``tw_vectors``.
    """
    return any(
        data or (new_length is not None)
        for (test, data, new_length)
        in tw_vectors.values()
    )