public function setLanguage($language = \Genesis\API\Constants\i18n::EN)
    {
        // Strip the input down to two letters
        $language = substr(strtolower($language), 0, 2);

        if (!\Genesis\API\Constants\i18n::isValidLanguageCode($language)) {
            throw new \Genesis\Exceptions\InvalidArgument(
                'The provided argument is not a valid ISO-639-1 language code!'
            );
        }

        $this->setApiConfig(
            'url',
            $this->buildRequestURL(
                'wpf',
                sprintf('%s/wpf', $language),
                false
            )
        );

        return $this;
    }