To use the packages you would need to install them. Depending on your setup this can vary. Based on your tags, I am assuming you're pip-installing packages. You need to run the following commands to install the packages:

1. pip install Flask (https://pypi.org/project/Flask/)
2. pip install requests (https://pypi.org/project/requests/)
3. pip install transformers (https://pypi.org/project/transformers/)

Once you install these packages, ideally your errors should be resolved.