Serve a JSON object containing some base properties used by the frontend.

    * data_location is either a path to a directory or an address to a
      database (depending on which mode TensorBoard is running in).
    * window_title is the title of the TensorBoard web page.

def _serve_environment(self, request):
    """Serve a JSON object containing some base properties used by the frontend.

    * data_location is either a path to a directory or an address to a
      database (depending on which mode TensorBoard is running in).
    * window_title is the title of the TensorBoard web page.
    """
    return http_util.Respond(
        request,
        {
            'data_location': self._logdir or self._db_uri,
            'mode': 'db' if self._db_uri else 'logdir',
            'window_title': self._window_title,
        },
        'application/json')