Getting error when i train multiple classes using yolov2object detector

Hello i train multiple classes.first i label the data using image labeler.

But i am getting the following error

Conversion from cell failed. Element 1 must be convertible to a

string scalar.

Error in trainYOLOv2ObjectDetector>iCheckGroundTruth (line 362)

I = imread(string(row{1,1}));

Error in trainYOLOv2ObjectDetector>iParseInputsYolov2 (line 279)

[trainingData, validTrainingData] =

iCheckGroundTruth(trainingData, useParallel);

Error in trainYOLOv2ObjectDetector (line 174)

[trainingData, lgraph, params, options] = iParseInputsYolov2(...

Error in train1 (line 62)

[detector1,info] =

trainYOLOv2ObjectDetector(trainingdata,lgraph,options);