refactor: avoid parsing document twice for figure numbers

test/test_html_slides.py

@@ -3,9 +3,9 @@ import random
 
 import pytest
 from jinja2 import Environment, FileSystemLoader
-from mistletoe import Document
 
 import src.config as config
+from renderer.document import Document
 from renderer.fifty_ohm_html_slide_renderer import FiftyOhmHtmlSlideRenderer
 
 conf = config.Config()