SV* set_parent(SV* self, SV* parent) {
          Node* me = (Node*)SvIV(SvRV(self));
          SvREFCNT_inc(parent);
          if (me->parent)
              SvREFCNT_dec(me->parent);
          me->parent = parent;
          SvREFCNT_inc(self);
          return self;
	}