boolean transactionInFlight() {
        return transactionInFlight;
    }
{@code StreamsProducer} manages the producers within a Kafka Streams application.
<p>
If EOS is enabled, it is responsible to init and begin transactions if necessary.
It also tracks the transaction status, ie, if a transaction is in-fight.
<p>
For non-EOS, the user should not call transaction related methods.
streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsProducer.java