@Test
public void multiGroupKey() {
TableModelDescription desc = new TableModelBuilder("A")
.add(null, "sex", PropertyTypeKind.BYTE)
.add(null, "age", PropertyTypeKind.SHORT)
.add(null, "name", new StringType(255))
.toDescription();
SummarizedModelDescription model = new SummarizedModelBuilder("S", desc, "a")
.add("sex", Aggregator.IDENT, "sex")
.add("age", Aggregator.IDENT, "age")