add a statement identifying StringI and StringO objects.

diff --git a/Doc/lib/libstringio.tex b/Doc/lib/libstringio.tex
index c268690ea0d56141cfeec5cedf7e0ee8cf17a13b..f78d016e0c73c2752b79f540a41aa7e7553a1674 100644 (file)
--- a/Doc/lib/libstringio.tex
+++ b/Doc/lib/libstringio.tex
@@ -62,7 +62,8 @@ strings that cannot be encoded as plain \ASCII{} strings.
 Another difference from the \refmodule{StringIO} module is that calling
 \function{StringIO()} with a string parameter creates a read-only object.
 Unlike an object created without a string parameter, it does not have
-write methods.
+write methods.  These objects are not generally visible.  They turn up in
+tracebacks as \class{StringI} and \class{StringO}.
 
 The following data objects are provided as well: