anchor.diff:                return req.parseQuery().then((query) {
                   return this.modify(
                       parseId(req.params['id']),
  -                    body,
  +                    body as Data,
                       mergeMap([
                         {'query': query},
                         restProvider,
  
positive.code:         return req.parseBody().then((body) {
            return this
                .create(
                    body,
                    mergeMap([
                      {'query': query},
                      restProvider,
  
negative.code:   }
  
    /// Retrieves the desired resource.
    Future read(Id id, [Map params]) {
      throw new AngelHttpException.methodNotAllowed();
    }
  
    /// Creates a resource.
    Future create(Data data, [Map params]) {
      throw new AngelHttpException.methodNotAllowed();
    }
  
    /// Modifies a resource.
    Future modify(Id id, Data data, [Map params]) {
      throw new AngelHttpException.methodNotAllowed();
    }
  
    /// Overwrites a resource.
    Future update(Id id, Data data, [Map params]) {
      throw new AngelHttpException.methodNotAllowed();
    }
  
    /// Removes the given resource.
    Future remove(Id id, [Map params]) {
      throw new AngelHttpException.methodNotAllowed();
    }
  
  