def build_train_loader(cls, cfg):
        """
        Returns:
            iterable
        It now calls :func:`fastreid.data.build_reid_train_loader`.
        Overwrite it if you'd like a different data loader.
        """
        logger = logging.getLogger("fastreid.clas_dataset")
        logger.info("Prepare training set")

        train_items = list()
        for d in cfg.DATASETS.NAMES:
            data = DATASET_REGISTRY.get(d)(root=_root)
            if comm.is_main_process():
                data.show_train()
            train_items.extend(data.train)
        transforms = build_transforms(cfg, is_train=True)
        train_set = ClasDataset(train_items, transforms)
        cls.idx2class = train_set.idx_to_class

        data_loader = build_reid_train_loader(cfg, train_set=train_set)
        return data_loader

        Returns:
            iterable
        It now calls :func:`fastreid.data.build_reid_train_loader`.
        Overwrite it if you'd like a different data loader.
        
projects/FastClas/fastclas/trainer.py