def _check_exists(self):
        """Check the exists of data files."""
        root = self.data_prefix['root']

        for filename, _ in (self.train_list + self.test_list):
            # get extracted filename of data
            extract_filename = rm_suffix(filename)
            fpath = join_path(root, extract_filename)
            if not exists(fpath):
                return False
        return True
Check the exists of data files.
mmpretrain/datasets/mnist.py