def METHOD_NAME(units, gds_filename):
    gds_absname = os.path.realpath(gds_filename)
    k = (units, gds_absname)
    try:
        return _GDS_READER_CACHE[k]
    except KeyError:
        debug.info(4, "Creating VLSI layout from {}".format(gds_absname))
        cell_vlsi = gdsMill.VlsiLayout(units=units)
        reader = gdsMill.Gds2reader(cell_vlsi)
        reader.loadFromFile(gds_absname, special_purposes)
        _GDS_READER_CACHE[k] = cell_vlsi
        return cell_vlsi