flatMapTuple2<E, A, B>  function 
 
        
TaskEither<E, dynamic>  Function(TaskEither<E, A> )
flatMapTuple2<E, A, B>( 
    
    
- TaskEither<E, B> f(- A a
 
Implementation
TaskEither<E, Tuple2<A, B>> Function(TaskEither<E, A>) flatMapTuple2<E, A, B>(
        TaskEither<E, B> Function(A a) f) =>
    flatMap((a) => f(a).p(map((b) => tuple2(a, b))));