code: public final <V, C> Flux<T> distinct(
  			Function<? super T, ? extends V> keySelector,
  			Supplier<C> distinctStoreSupplier,
  			BiPredicate<C, V> distinctPredicate,
  			Consumer<C> cleanup) {
  		if (this instanceof Fuseable) {
  			return onAssembly(new FluxDistinctFuseable<>(this, keySelector,
  					distinctStoreSupplier, distinctPredicate, cleanup));
  		}
  		return onAssembly(new FluxDistinct<>(this, keySelector, distinctStoreSupplier, distinctPredicate, cleanup));
  	}
docs: For each {@link Subscriber}, track elements from this {@link Flux} that have been
  seen and filter out duplicates, as compared by applying a {@link BiPredicate} on
  an arbitrary user-supplied {@code <C>} store and a key extracted through the user
  provided {@link Function}. The BiPredicate should typically add the key to the
  arbitrary store for further comparison. A cleanup callback is also invoked on the
  store upon termination of the sequence.
  
  <p>
  <img class="marble" src="doc-files/marbles/distinctWithKey.svg" alt="">
  
  @reactor.discard This operator discards elements that don't match the distinct predicate,
  but you should use the {@code cleanup} as well if you need discarding of keys
  categorized by the operator as "seen".
  
  @param keySelector function to compute comparison key for each element
  @param distinctStoreSupplier supplier of the arbitrary store object used in distinct
  checks along the extracted key.
  @param distinctPredicate the {@link BiPredicate} to apply to the arbitrary store +
  extracted key to perform a distinct check. Since nothing is assumed of the store,
  this predicate should also add the key to the store as necessary.
  @param cleanup the cleanup callback to invoke on the store upon termination.
  
  @param <V> the type of the key extracted from each value in this sequence
  @param <C> the type of store backing the {@link BiPredicate}
  
  @return a filtering {@link Flux} only emitting values with distinct keys