ethod should return a new iterator object that

            can iterate over all the objects in the container. For mappings,

            it should iterate over the keys of the container, and should 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 ``<