pub fn make_from(trace: Tr) -> (Self, Rc<RefCell<TraceBox<Tr>>>) {

        let wrapped = Rc::new(RefCell::new(TraceBox::new(trace)));

        let handle = TraceRc {
            logical_compaction: wrapped.borrow().logical_compaction.frontier().to_owned(),
            physical_compaction: wrapped.borrow().physical_compaction.frontier().to_owned(),
            wrapper: wrapped.clone(),
        };

        (handle, wrapped)
    }
Allocates a new handle from an existing wrapped wrapper.
differential-dataflow/src/trace/wrappers/rc.rs