def test_modify_view_component(matrix_type, mapping_name):
    adata = ad.AnnData(
        np.zeros((10, 10)),
        **{mapping_name: dict(m=matrix_type(asarray(sparse.random(10, 10))))},
    )
    init_hash = joblib.hash(adata)

    subset = adata[:5, :][:, :5]
    assert subset.is_view
    m = getattr(subset, mapping_name)["m"]
    m[0, 0] = 100
    assert not subset.is_view
    assert getattr(subset, mapping_name)["m"][0, 0] == 100

    assert init_hash == joblib.hash(adata)
def union(matches, root, cwd):
    """Union a list of matchers.

    If the list is empty, return nevermatcher.
    If the list only contains one non-None value, return that matcher.
    Otherwise return a union matcher.
    """
    matches = list(filter(None, matches))
    if len(matches) == 0:
        return nevermatcher(root, cwd)
    elif len(matches) == 1:
        return matches[0]
    else:
        return unionmatcher(matches)