protected function formatContext(array $vars, array $context)
    {
        // Set top-level data in the 'context', merging to get those keys in front
        $context = array_merge([
            'timestamp' => $this->stringify($vars['datetime']),
            'channel'   => $this->stringify($vars['channel']),
            'severity'  => $this->stringify($vars['level_name']),
            'level'     => $vars['level'],
            'message'   => $vars['message'],
        ], $context);

        return $this->stringify($context) . "\n";
    }