@Override
    public boolean equals(final Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        final PutOutcome that = (PutOutcome) o;
        return isSuccess == that.isSuccess &&
                Objects.equals(isDuplicate, that.isDuplicate);
    }
@return An optional that states whether the entry put was a duplicate of
an existing key, if known.
stroom-lmdb/src/main/java/stroom/lmdb/PutOutcome.java