def fname_chunk_tag(chunk_bounds):
    """ Creates a filename tag for a 3d dataset chunk """
    chunk_min = chunk_bounds.min()
    chunk_max = chunk_bounds.max()
    return "{0}_{1}_{2}-{3}_{4}_{5}".format(chunk_min[0], chunk_min[1],
                                            chunk_min[2],
                                            chunk_max[0], chunk_max[1],
                                            chunk_max[2])