new OuterPOJO(new POJO("key2", 2L, "value3")), new OuterPOJO(new POJO("key2", 2L, "value4")))) .apply(Group.byFieldAccessDescriptor(groupKeys));
.apply(Create.of(elements)) .apply( Group.<OuterAggregate>byFieldAccessDescriptor(field2Selector) .aggregateFields(field1Selector, Sum.ofLongs(), "field1_sum") .aggregateFields(field3Selector, Sum.ofIntegers(), "field3_sum")