* Fix O(n) memory growth in PDF conversion by calling page.close() after each page
* Refactor PDF memory optimization tests for improved readability and consistency
* Add memory benchmarking tests for PDF conversion with page.close() fix
* Remove unnecessary blank lines in PDF memory optimization tests for cleaner code
* Bump version to 0.1.6b2 in __about__.py
* Update PDF conversion tests to include mimetype in StreamInfo
lesyk