ModuleNotFoundError: No module named 'pycocotools._mask'

This error occurs when the pycocotools package is not installed or not properly installed on your system.

To resolve this error, you can try the following steps:

1. Install pycocotools package using pip:

pip install pycocotools

2. If you have already installed pycocotools, then try upgrading it to the latest version:

pip install --upgrade pycocotools

3. If the above steps do not work, then you can try installing the package from the source:

git clone https://github.com/cocodataset/cocoapi.git
cd cocoapi/PythonAPI
make

4. After installing the package, make sure to add the path of the package to your PYTHONPATH environment variable:

export PYTHONPATH=/path/to/cocoapi/PythonAPI:$PYTHONPATH

5. Try running your code again and check if the error is resolved.