anchor.diff:          |> List.filter Option.isSome
           |> List.map Option.get
   
  +    let findOptionsToFs (o: FindOptions): FindOption list = 
  +        failwith "not implemented"
  +
       let dictToMap fn (dict: Dictionary<'a, 'b>) = 
           dict 
           |> Seq.map (fun kvp -> kvp.Key, fn kvp.Value)
  
positive.code:         | FromDesignDoc
          | FromDesignDocAndIndex
  
      type UsableIndex (designDocId: string, ?indexName: string) =
          member val DesignDocId = designDocId with get, set
          member val IndexName = (indexName |> Option.defaultValue "") with get, set
  
      type FindOptions(?useIndex) = 
          member val Fields: string list = [] with get, set
          member val SortBy: Sorting list = [] with get, set
          member val Limit = System.Nullable<int>() with get, set
  
negative.code:         failwith "Not implemented"
  
      member __.FindBySelectorAsync (dict, ?options): Task<IEnumerable<'doctype>> = 
          let opts = 
              options 
              |> Option.map findOptionsToFs
              |> Option.defaultValue []
  
          dict 
          |> dictToMap findExpressionToFs 
          |> find opts 
          <| client 
          |> Async.MapSeq toDoc
          |> task
  
      member __.CountAsync(): Task<int> = 
  