diff --git a/docs/conf.py b/docs/conf.py
index a59789272..85179bacf 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -94,11 +94,11 @@
 
 # -- sphinx_ext_graphviz options ---------------------------------------------
 
-graphviz_output_format = 'svg'  
+graphviz_output_format = "svg"
 inheritance_graph_attrs = dict(
     rankdir="LR",
     fontsize=14,
-    ratio='compress',
+    ratio="compress",
     # bgcolor='transparent',
 )