public function start(?string $groupCode = null): void;  	abstract protected function createValidatorInstance(mixed ...$fieldsToValidate): Validator;  	abstract protected function updateOrCreateItem(mixed ...$productFields): void;  	protected function logStatistics(): void 	{ 		Log::warning('failed imported items count', [$this->failedImportsCount]); 		Log::warning('failed imports validation errors', $this->failedImports); 		Log::warning('successful imports count', [$this->importedItemsCount]); 		Log::warning('failed sync items count', [$this->failedSyncItemsCount]); 		Log::warning('failed sync validation errors', $this->failedSyncs); 		Log::warning('successful sync items count', [$this->syncedItemsCount]); 	}