private function getVariationIdentifierByIdentifier($identifier)
    {
        $variations = $this->client->request('GET', 'items/variations', ['id' => $identifier]);

        if (!empty($variations)) {
            $variation = array_shift($variations);

            return $variation['id'];
        }

        return 0;
    }
private function getVariationIdentifierByIdentifier($identifier)
    {
        $variations = $this->client->request('GET', 'items/variations', ['id' => $identifier]);

        if (!empty($variations)) {
            $variation = array_shift($variations);

            return $variation['id'];
        }

        return 0;
    }
@param string $identifier

@return int