How to add group by condition into a LogicalAggregate in calcite?

Question

For a sql like :

select count(*) from T group by c1,c2; 

I parsed the sql to relnodes by apache calcite.what I'm trying to do is add a group by condition c3 to the relative LogicalAggregate and transform the sql to s

`elect count(*) from T group by c1,c2,c3;`

I'm wondering if there is any methods to edit a LogicalAggregate node. THX