Add a comment to indicate the methods of the StringIO are being discussed...

Doc/lib/libstrio.tex

@@ -13,6 +13,9 @@ to an existing string by passing the string to the constructor.
 If no string is given, the \class{StringIO} will start empty.
 \end{classdesc}
 
+The following methods of \class{StringIO} objects require special
+mention:
+
 \begin{methoddesc}{getvalue}{}
 Retrieve the entire contents of the ``file'' at any time before the
 \class{StringIO} object's \method{close()} method is called.

Doc/libstrio.tex

@@ -13,6 +13,9 @@ to an existing string by passing the string to the constructor.
 If no string is given, the \class{StringIO} will start empty.
 \end{classdesc}
 
+The following methods of \class{StringIO} objects require special
+mention:
+
 \begin{methoddesc}{getvalue}{}
 Retrieve the entire contents of the ``file'' at any time before the
 \class{StringIO} object's \method{close()} method is called.