public DataTable transpose() {
        if (raw instanceof TransposedRawDataTableView) {
            TransposedRawDataTableView transposed = (TransposedRawDataTableView) this.raw;
            return transposed.dataTable();
        }
        return new DataTable(new TransposedRawDataTableView(), tableConverter);
    }
@Test
    void repeated_transposition_yields_original_table() {
        DataTable table = createSimpleTable();
        assertSame(table, table.transpose().transpose());
    }