Document Ellipsis (not much of a documentation snippet, but at least

it's mentioned.

Doc/lib/libstdtypes.tex

@@ -692,6 +692,15 @@ object, named \code{None} (a built-in name).
 
 It is written as \code{None}.
 
+\subsubsection{The Ellipsis Object}
+\label{bltin-ellipsis-object}
+
+This object is used by extended slice notation (see the \emph{Python
+Reference Manual}).  It supports no special operations.  There is
+exactly one ellipsis object, named \code{Ellipsis} (a built-in name).
+
+It is written as \code{Ellipsis}.
+
 \subsubsection{File Objects}
 \label{bltin-file-objects}