return Maps.containsEntryImpl(delegate(), o);
      }
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      synchronized (mutex) {
        return Collections2.containsAllImpl(delegate(), c);
      }
    }

    @Override
    public boolean equals(@CheckForNull Object o) {
      if (o == this) {
        return true;
      }
      synchronized (mutex) {

        return Maps.containsEntryImpl(delegate(), o);
      }
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      synchronized (mutex) {
        return Collections2.containsAllImpl(delegate(), c);
      }
    }

    @Override
    public boolean equals(@CheckForNull Object o) {
      if (o == this) {
        return true;
      }
      synchronized (mutex) {