build: fix readthedocs visuals

Author: btorresgil

.readthedocs.yaml

@@ -10,6 +10,8 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.7"
+  apt_packages:
+    - graphviz
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:

docs/conf.py

@@ -127,10 +127,8 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-if on_rtd:
-    html_theme = "default"
-else:
-    html_theme = "sphinx_rtd_theme"
+html_theme = "sphinx_rtd_theme"
+if not on_rtd:
     html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 # Theme options are theme-specific and customize the look and feel of a