anchor.diff:  def writeFail(id: String, item: Item) : Future[Boolean] = Future { Thread.sleep(1000); println(id); throw new RuntimeException(id.toString) }
   ----
   
  -=== Transforming and traversing collections serially and concurrently
  +== Transforming and traversing collections serially and concurrently
   A common task when working with futures is either transforming or traversing a collection that will call a method that
   returns a future. The standard idiom for performing this task only provides methods for concurrent operation and, with
   enough nesting, leads to difficult to read code:
  
positive.code: ----
  
  
  === Imports for Examples
  All code examples assume the following imports:
  [source,scala,numbered]
  ----
  
negative.code:       println("Writing...")
        oomNewItemBatch.workers(2).flatMap(_.workers(4).map(item => write(item.id, item)))
      }
    } yield oomResult.forall(_ == true)
  }
  ----
  
  == Tuple Concurrently
  When first using +Future+ with a for-comprehension, it is natural to assume the following will produce concurrent
  operation:
  
  