public function setThumbnail($data, $encode = true)
    {
        if ($encode && ! base64_decode($data, $strict = true)) {
            // If the string we're given is not base 64 encoded, then
            // we will encode it before setting it on the user.
            $data = base64_encode($data);
        }

        return $this->setAttribute($this->schema->thumbnail(), $data);
    }