public function setCredentials($name = null)
    {
        // No name given.
        if (is_null($name)) {
            $name = config('personality-insights.default_credentials');
        }

        // Credentials does not exist.
        if (! config()->has('personality-insights.credentials.'.$name)) {
            throw new InvalidCredentialsName;
        }

        $this->credentials = config('personality-insights.credentials.'.$name);

        return $this;
    }