which it knows as ``this_room``, and which it then uses to test for the
``visited`` attribute. On the second line we supply ``location`` as the
argument, but the routine just sees another value in its ``this_room``
which it knows as ``this_room``, and which it then uses to test for the
``visited`` attribute. On the second line we supply ``location`` as the
argument, but the routine just sees another value in its ``this_room``