code: def register_mime(shortname, mime_types):
      
      if shortname in _MIME_TYPES:
          raise MimeRenderException('"%s" has already been registered'%shortname)
      _MIME_TYPES[shortname] = mime_types
docs: Register a new mime type.
      Usage example:
          mimerender.register_mime('svg', ('application/x-svg', 'application/svg+xml',))
      After this you can do:
          @mimerender.mimerender(svg=render_svg)
          def GET(...
              ...