Description : generate list for lip images

def _list_images(self, root):
        """
        Description : generate list for lip images
        """
        self.labels = []
        self.items = []

        valid_unseen_sub_idx = [1, 2, 20, 22]
        skip_sub_idx = [21]

        if self._mode == 'train':
            sub_idx = ['s' + str(i) for i in range(1, 35) \
                             if i not in valid_unseen_sub_idx + skip_sub_idx]
        elif self._mode == 'valid':
            sub_idx = ['s' + str(i) for i in valid_unseen_sub_idx]

        folder_path = []
        for i in sub_idx:
            folder_path.extend(glob.glob(os.path.join(root, i, "*")))

        for folder in folder_path:
            filename = glob.glob(os.path.join(folder, "*"))
            if len(filename) != self._seq_len:
                continue
            filename.sort()
            label = os.path.split(folder)[-1]
            self.items.append((filename, label))