def METHOD_NAME(xy_of_hex, at):
    perimeter_links = [[0, 1], [1, 2], [2, 5], [5, 8], [8, 7], [7, 6], [6, 3], [3, 0]]
    graph = VoronoiDelaunayToGraph(xy_of_hex, perimeter_links=perimeter_links)
    ids = []
    for name in graph.ids_with_prefix(at):
        ids.append(np.sort(np.unique(getattr(graph, name).reshape((-1,)))))
    ids = np.sort(np.unique(np.concatenate(ids)))
    ids = ids[ids >= 0]
    assert ids[0] >= 0
    assert ids[-1] <= graph._mesh.dims[at]