code: @GwtIncompatible("incompatible method")
      private static void unregister(final Object lhs, final Object rhs) {
          final Set<Pair<IDKey, IDKey>> registry = getRegistry();
          if (registry != null) {
              final Pair<IDKey, IDKey> pair = getRegisterPair(lhs, rhs);
              registry.remove(pair);
              if (registry.isEmpty()) {
                  REGISTRY.remove();
              }
          }
      }
docs: <p>
  Unregisters the given object pair.
  </p>
  
  <p>
  Used by the reflection methods to avoid infinite loops.
  
  @param lhs <code>this</code> object to unregister
  @param rhs the other object to unregister
  @since 3.0