anchor.diff:  // Find all the optional properties on ships. Append a question mark after the
   // property name to signify that the property is optional.
   para {
  -  let obj = ParaValue.Parse data
  +  let obj = ParaValue.Parse patrolData
     let! ships = obj / "ship" |> ParaValue.flatMap asRecord
     let required, optional = findOptional ships
     required |> Seq.iter (printfn "%s")
  
positive.code: | Error(error) -> printfn "%s" error
  
  // In reality the code may be written like:
  ParaValue.Parse data
  |> ParaValue.collect "ship"
  |> ParaValue.flatMap parseShip
  |> ParaResult.map (Array.sortByDescending snd)
  
negative.code:   return name, strength
  }
  
  // Collect all the values with a key "ship" into a ParaValue.Array
  let (pips : ParaValue) = ParaValue.collect "ship" shipsObj
  
  // Execute `parseShip` on each ship and aggregate the result
  // into an array
  