diff --git a/src/lclayout/graphrouter/inspect.py b/src/lclayout/graphrouter/inspect.py
index 56f6945ddd45987219cc62498ae30f295bc98693..2d053c62b66eb6e0f988fc42de3dd4ad69d01653 100644
--- a/src/lclayout/graphrouter/inspect.py
+++ b/src/lclayout/graphrouter/inspect.py
@@ -70,6 +70,7 @@ class InspectRouter(GraphRouter):
                 pos[n] = (x, y)
                 
         def hue2rgb(hue: float) -> str:
+            # Create a HTML color code from a hue value.
             assert 0. <= hue <= 1.
 
             a = 2 * math.pi / 3