return obverse.keySet();
    }

    @LazyInit private transient Set<Entry<V, K>> inverseEntrySet;

    @Override
    public Set<Entry<V, K>> entrySet() {
      Set<Entry<V, K>> result = inverseEntrySet;
      return (result == null) ? inverseEntrySet = new InverseEntrySet<>(obverse) : result;
    }

    @GwtIncompatible("serialization")