 
     /**
      * Maps `Observable`'s error if the `Result` is `.failure` while ignoring value accompanied with `.success`.
+     * - parameter transform: closure to use when transforming error
+     * - returns: `Observable` of type `Result` and its `.failure` errors transformed using the passed closure
      * ## Example
      * ```
      * httpObservable.mapError { error in


    /**
     * Filters `Observable` to block successful `Result`s while mapping the `Observable` to the error of `.failure` that pass.
     * ## Example
     * ```
     * httpObservable.errorOnly()


    /**
     * `Result` equivalent of `Observable`'s `flatMap` only affecting `.success` value.
     * - parameter selector: closure to use when transforming value into `Observable`
     * - returns: `Observable` of type `Result` and its `.success` values transformed using the passed closure
     * - NOTE: See `mapValue(_:)` and [FlatMap operator](http://reactivex.io/documentation/operators/flatmap.html).
     */
    public func flatMapValue<O>(_ selector: @escaping (E.Value) -> O) -> Observable<Result<O.E, E.Error>> where O : ObservableConvertibleType {
