ModuleNotFoundError: No module named 'pycocotools._mask'

This error occurs when the pycocotools library is not installed properly or when there is a version mismatch between the library and the Python version being used.

To resolve this error, try reinstalling the pycocotools library by running the following command in the terminal:

pip install pycocotools

If this does not work, try upgrading the pip package manager by running the following command:

pip install --upgrade pip

Then reinstall the pycocotools library as mentioned above.

If the error still persists, try installing the library from the source code available on the official GitHub repository: https://github.com/cocodataset/cocoapi.