code: def media(self):
          
          media = super(ChainedSelectMultiple, self).media
          js = ['smart-selects/admin/js/chainedm2m.js',
                'smart-selects/admin/js/bindfields.js']
          if self.horizontal:
              # For horizontal mode add django filter horizontal javascript code
              js.extend(["admin/js/core.js",
                         "admin/js/SelectBox.js",
                         "admin/js/SelectFilter2.js"])
          media += Media(js=js)
          return media
docs: Media defined as a dynamic property instead of an inner class.