Use \code{True} (or False) instead of true/false.
Not sure if code is correct, but that is what's in this file.
I've seen \constant{True} in other places.
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index f7db943..761acd3 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -547,8 +547,8 @@
\end{methoddesc}
\begin{methoddesc}[string]{endswith}{suffix\optional{, start\optional{, end}}}
-Return true if the string ends with the specified \var{suffix},
-otherwise return false. With optional \var{start}, test beginning at
+Return \code{True} if the string ends with the specified \var{suffix},
+otherwise return \code{False}. With optional \var{start}, test beginning at
that position. With optional \var{end}, stop comparing at that position.
\end{methoddesc}
@@ -678,8 +678,8 @@
\begin{methoddesc}[string]{startswith}{prefix\optional{,
start\optional{, end}}}
-Return true if string starts with the \var{prefix}, otherwise
-return false. With optional \var{start}, test string beginning at
+Return \code{True} if string starts with the \var{prefix}, otherwise
+return \code{False}. With optional \var{start}, test string beginning at
that position. With optional \var{end}, stop comparing string at that
position.
\end{methoddesc}