presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/credential/ExtraCredentialProvider.java/ExtraCredentialProvider/ExtraCredentialProvider
class ExtraCredentialProvider:    public ExtraCredentialProvider(Optional<String> userCredentialName, Optional<String> passwordCredentialName, CredentialProvider delegate)
    {
        this.delegate = requireNonNull(delegate, "delegate is null");
        this.userCredentialName = requireNonNull(userCredentialName, "userCredentialName is null");
        this.passwordCredentialName = requireNonNull(passwordCredentialName, "passwordCredentialName is null");
    }