code: def get_auth_url(self, app_id, canvas_url, perms=None, **kwargs):
          
          url = "{0}{1}/{2}".format(
              FACEBOOK_WWW_URL, self.version, FACEBOOK_OAUTH_DIALOG_PATH
          )
  
          args = {"client_id": app_id, "redirect_uri": canvas_url}
          if perms:
              args["scope"] = ",".join(perms)
          args.update(kwargs)
          return url + urlencode(args)
docs: Build a URL to create an OAuth dialog.