Adding groups programmatically using node_import

We are creating a commons site that will have around 600 active groups. In order to not have to enter them manually I have testes node_import and it works well, however as far as I know, there is not an option to identify the group as a subgroup or which group should be it's parent.

Is there a way to handle this or do I need to do this manually on all the groups.

Thx John