question: public final ParallelFlux < T > filter ( Predicate < ? super T > predicate ) { Objects . requireNonNull ( predicate , "predicate" ) ; return onAssembly ( new ParallelUnorderedFilter < > ( this , predicate ) ) ; }
target:  Filters the source values on each 'rail'. <p> Note that the same predicate may be called from multiple threads concurrently.