    def get_user(self, handler, *, sync=True):
        """Get the Hub user for a given tornado handler.

        Checks cookie with the Hub to identify the current user.

        .. versionadded:: 2.4
            async support via `sync` argument.

        Args:
            handler (tornado.web.RequestHandler): the current request handler
            sync (bool): whether to block for the result or return an awaitable

        Returns:
            user_model (dict): The user model, if a user is identified, None if authentication fails.

            The 'name' field contains the user's name.
        """
        return self._call_coroutine(sync, self._get_user, handler)
Get the Hub user for a given tornado handler.

Checks cookie with the Hub to identify the current user.

.. versionadded:: 2.4
async support via `sync` argument.

Args:
handler (tornado.web.RequestHandler): the current request handler
sync (bool): whether to block for the result or return an awaitable

Returns:
user_model (dict): The user model, if a user is identified, None if authentication fails.

The 'name' field contains the user's name.
jupyterhub/services/auth.py