TODO Mock pdfium unavailable for lattice test

[bosd]

To improve coverage of the pdfium backend, would like to add a mock the availability.

What is the proper way to do it?

[stefan6419846]

I personally would avoid modifying sys.modules etc. on the main thread and instead move this to a corresponding subprocess (example: https://github.com/py-pdf/pypdf/blob/98aa9742e757ec428e1953ba7f47c6d7c44b331a/tests/test_filters.py#L248-L291). Nevertheless, this might require further configuration for coverage.