Explained more clearly why it's okay for interface classes to be keys.

This commit sponsored by Nick Glynn.  Thank you!

diff --git a/docs/source/pluginwriter/api.rst b/docs/source/pluginwriter/api.rst
index 3bb5f445e98fa594224b3fd62f865008135ebf54..66def1730b163332a5f8fac3b4cc334fdab6d4dc 100644 (file)
--- a/docs/source/pluginwriter/api.rst
+++ b/docs/source/pluginwriter/api.rst
@@ -273,7 +273,9 @@ Just write the interface like so::
 
 
 It's fine to use your interface as the key instead of a string if you
-like.
+like.  (Usually this is messy, but since interfaces are public and
+since you need to import them into your plugin anyway, interfaces
+might as well be keys.)
 
 Then a plugin providing your interface can be like::