1 files changed, 13 insertions, 1 deletions
diff --git a/mu4web/html_render.py b/mu4web/html_render.py
index fc608fb..f9c9aa8 100644
--- a/mu4web/html_render.py
+++ b/mu4web/html_render.py
@@ -1,5 +1,15 @@
+"""
+Render python structures into HTML strings.
+
+Instead of constructing HTML strings manually or through templates,
+instead write python structures, and serialize them at the last
+possible moment. See ``render_document`` for a detailed explanation of
+valid types.
+"""
+
 import html
 from typing import (
+    Any,
     Callable,
     Union,
 )
@@ -11,7 +21,9 @@ except ImportError:
 # TODO compare this against xml.etree.ElementTree, which appears to
 # have a HTML mode.
 
-HTML: TypeAlias = Union[tuple,
+# ``tuple[Any, ...]`` should really be ``tuple['HTML', ...]``, but
+# that doesn't work for some reason.
+HTML: TypeAlias = Union[tuple[Any, ...],
                         list['HTML'],
                         Callable[[], str],
                         None, str, int, float]