code: public synchronized SlabRef detach() {
          if (!isAttached()) {
              return null;
          }
  
          // Pass ownership of the slab ref to the caller.  No need to call slab.release().
          SlabRef slab = _slab;
          _slab = null;
          _slabExpiresAt = 0;
          return slab;
      }
docs: Detaches a slab from the channel and returns it to the caller to dispose of.