Image Classifier error?

I write this

categoryClassifier = trainImageCategoryClassifier(trainingset,bag);

and I get

Error using imageCategoryClassifier Expected imgSets to be one of these types:

imageSet

Instead its type was matlab.io.datastore.ImageDatastore.****

when I try

categoryClassifer = trainImageCategoryClassifier(imageSet(trainingset.Files,bag);

I get

Error using imageSet/parseInput (line 93) Too many input arguments.

Error in imageSet (line 288) this = parseInput(this, varargin{:});

that's it. what should I do.