Gets a GoSubDag initialized for use by a Grouper object.

def get_gosubdag(gosubdag=None):
        """Gets a GoSubDag initialized for use by a Grouper object."""
        if gosubdag is not None:
            if gosubdag.rcntobj is not None:
                return gosubdag
            else:
                gosubdag.init_auxobjs()
                return gosubdag
        else:
            go2obj = get_godag()
            return GoSubDag(None, go2obj, rcntobj=True)