code: public static <T extends RefCounted<T>> Refs<T> tryRef(Iterable<T> reference)
      {
          HashMap<T, Ref<T>> refs = new HashMap<>();
          for (T rc : reference)
          {
              Ref<T> ref = rc.tryRef();
              if (ref == null)
              {
                  release(refs.values());
                  return null;
              }
              refs.put(rc, ref);
          }
          return new Refs<T>(refs);
      }
docs: Acquire a reference to all of the provided objects, or none