d also
            be made available as the method <tt class=
            "method">iterkeys()</tt>. 
            <p>
              Iterator objects also need to implement this method; they are
              required to return themselves. For more information on iterator
              objects, see ``<a class="ulink" href=
              "http://www.python.org/doc/current/lib/typeiter.html">Iterator
              Types</a>'' in the <em class="citetitle"><a href=
              "http://www.python.org/doc/current