Is it possible to use Publisher created using Java 9 Reactive Stream in Spring WebFlux BodyInserters?

Question

I am learning reactive programming using Reactive Streams in Java 9 and also using org.reactivestreams in spring 5.

And i am creating a WebClient using the webflux api spring 5 and spring boot2.

Now, when we set the body of a request using webclient, we can pass on a Reactive Stream(org.reactivestreams in spring 5 to be specific) in the BodyInserters methods as follows:

WebClient.RequestHeadersSpec<?> requestSpec1 = WebClient
                                                .create()
                                                .method(HttpMethod.POST).uri("/getDocs")
                                                .body(BodyInserters
                                                .fromPublisher(Mono.just("data"), 
                                                                String.class)
                                                );

and from fromPublisher method definition:

Return a BodyInserter that writes the given Publisher.

Parameters: publisher the publisher to stream to the response body elementClass the class of elements contained in the publisher

Now, the publishers and subcribers are also in java 9 reactive streams, and one of the publisher which i have created is like:

import java.util.List;
import java.util.concurrent.SubmissionPublisher;

public class TestReactiveStreams {

    public static SubmissionPublisher<String> publisher;

    public static void main(String...strings ) {
        publisher = new SubmissionPublisher();
        TestSubscriber<String> subscriber = new TestSubscriber<String>();
        publisher.subscribe(subscriber);

        List<String> items = List.of("1","x","2","x","3","x");

        System.out.println("Subscribers = "+publisher.getNumberOfSubscribers());

        if(publisher.getNumberOfSubscribers() > 0) {
            items.stream().forEach(p -> publisher.submit(p));
        }

        publisher.close();


        try {
            Thread.currentThread().sleep(1000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        System.out.println("Consumed Elements = "+subscriber.consumed);

    }


}

Now my question is: Is it possible to use the publisher from TestReactiveStreams in the fromPublisher method of BodyInserters?

I tried the following:

BodyInserter<Publisher<String>, ReactiveHttpOutputMessage> inserter2 = BodyInserters
                .fromPublisher(TestReactiveStreams.publisher, SubmissionPublisher.class);

But this is giving the following compile time error:

The method fromPublisher(P, Class<T>) in the type BodyInserters is not applicable for the arguments 
 (SubmissionPublisher<String>, Class<SubmissionPublisher>)

Please suggest, how can we achieve this?