private static AbstractConscryptEngine toConscrypt(SSLEngine engine) {
        if (!isConscrypt(engine)) {
            throw new IllegalArgumentException(
                    "Not a conscrypt engine: " + engine.getClass().getName());
        }
        return (AbstractConscryptEngine) engine;
    }
Indicates whether the given {@link SSLEngine} was created by this distribution of Conscrypt.
common/src/main/java/org/conscrypt/Conscrypt.java