Document __unicode__. Fixes #541245.
diff --git a/Doc/ref/ref3.tex b/Doc/ref/ref3.tex
index 2056a6c..8dbe8f0 100644
--- a/Doc/ref/ref3.tex
+++ b/Doc/ref/ref3.tex
@@ -1096,6 +1096,13 @@
\withsubitem{(mapping object method)}{\ttindex{__len__()}}
\end{methoddesc}
+\begin{methoddesc}[object]{__unicode__}{self}
+Called to implement \function{unicode()}\bifuncindex{unicode} builtin;
+should return a Unicode object. When this method is not defined, string
+conversion is attempted, and the result of string conversion is converted
+to Unicode using the system default encoding.
+\end{methoddesc}
+
\subsection{Customizing attribute access\label{attribute-access}}