no need to elaborate "string".

Doc/lib/libfuncs.tex

@@ -468,7 +468,7 @@ class C:
   Construct a list from those elements of \var{list} for which
   \var{function} returns true.  \var{list} may be either a sequence, a
   container which supports iteration, or an iterator,  If \var{list}
-  is a string (either \code{str} or \code{unicode}) or a tuple, the result
+  is a string or a tuple, the result
   also has that type; otherwise it is always a list.  If \var{function} is
   \code{None}, the identity function is assumed, that is, all elements of
   \var{list} that are false are removed.