code: public <B> OptionalT<W,B> flatMapT(final Function<? super T, OptionalT<W,B>> f) {
          return of(run.map(Optional -> Optional.flatMap(a -> f.apply(a).run.stream()
                                                                        .toList()
                                                                        .get(0))));
      }
docs: Flat Map the wrapped Optional
  <pre>
  {@code
  OptionalWT.of(AnyM.fromStream(Arrays.asOptionalW(10))
  .flatMap(t->Optional.completedOptional(20));
  
  
  //OptionalWT<AnyMSeq<Stream<Optional[20]>>>
  }
  </pre>
  @param f FlatMap function
  @return OptionalWT that applies the flatMap function to the wrapped Optional