def METHOD_NAME(tmpdir):
    ds = xr.Dataset({"a": (["time", "x"], np.ones((200, 10)))})
    tiles = []
    for i in range(1, 7):
        path = f"{tmpdir}/a.tile{i}.nc"
        ds.to_netcdf(path)
        tiles.append(path)
    out = open_tiles(tiles, str(tmpdir), chunks=TEST_CHUNKS)
    saved_ds = list(out)[0]
    assert isinstance(saved_ds, xr.Dataset)
    # check for variable "a"
    saved_ds["a"]