Do steps:
Before starting annotation, put image folder into the Images folder. Let my image folder name be pics, Project folder should be like this:
-main.py
-process.py
-classes.txt
-Images/
-pics/
-<image1>.png
-<image2>.png
-<image3>.png
-...
-Labels/
-pics/
Run below code with Python3
main.py
After running main.py, specify the image folder name that you put into Images folder. Just type pics into the Image Dir text box.
Before annotating bounding boxes, choose which class to annotate.
The dataset is ready for yolo training.