private function getNumberFromVariation($variationId)
    {
        static $variations;

        if (!isset($variations[$variationId])) {
            $response = $this->client->request('GET', 'items/variations', ['id' => $variationId]);

            if (empty($response)) {
                $variations[$variationId] = null;

                return $variations[$variationId];
            }

            $variation = array_shift($response);

            $variations[$variationId] = $variation['number'];
        }

        return $variations[$variationId];
    }
private function getNumberFromVariation($variationId)
    {
        static $variations;

        if (!isset($variations[$variationId])) {
            $response = $this->client->request('GET', 'items/variations', ['id' => $variationId]);

            if (empty($response)) {
                $variations[$variationId] = null;

                return $variations[$variationId];
            }

            $variation = array_shift($response);

            $variations[$variationId] = $variation['number'];
        }

        return $variations[$variationId];
    }
@param int $variationId

@return string