public function getById($stockistId)
    {
        if (!isset($this->instances[$stockistId])) {

            /** @var \Limesharp\Stockists\Api\Data\StockistInterface|\Magento\Framework\Model\AbstractModel $stockist */
            $stockist = $this->stockistInterfaceFactory->create();
            $this->resource->load($stockist, $stockistId);
            
            if (!$stockist->getId()) {
                throw new NoSuchEntityException(__('Requested stockist doesn\'t exist'));

           }
            $this->instances[$stockistId] = $stockist;
        }

        return $this->instances[$stockistId];;
    }