con.concat_examplesを使ってうまくデータを分けられない。

前提・実現したいこと

自分で持っている画像をchinerで使えるデータセットに変換し、con.concat_examplesを使ってデータを分割したいのですが、以下のようなエラーが発生します。

発生している問題・エラーメッセージ

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-26-3d8accadaf6d> in <module>()
----> 1 xtrain, ttrain = con.concat_examples(train)
      2 xtest, ttest = con.concat_examples(train)

7 frames
/usr/local/lib/python3.6/dist-packages/chainer/dataset/convert.py in __call__(self, *args, **kwargs)
     63         elif 'device' in kwargs:
     64             kwargs['device'] = _get_device(kwargs['device'])
---> 65         return base_callable(*args, **kwargs)
     66 
     67 

/usr/local/lib/python3.6/dist-packages/chainer/dataset/convert.py in concat_examples_func(batch, device, padding)
    271         raise ValueError('batch is empty')
    272 
--> 273     first_elem = batch[0]
    274 
    275     if isinstance(first_elem, tuple):

/usr/local/lib/python3.6/dist-packages/chainer/dataset/dataset_mixin.py in __getitem__(self, index)
     65             return [self.get_example(i) for i in index]
     66         else:
---> 67             return self.get_example(index)
     68 
     69     def __len__(self):

/usr/local/lib/python3.6/dist-packages/chainer/datasets/sub_dataset.py in get_example(self, i)
     74         if self._order is not None:
     75             index = self._order[index]
---> 76         return self._dataset[index]
     77 
     78 

/usr/local/lib/python3.6/dist-packages/chainer/dataset/dataset_mixin.py in __getitem__(self, index)
     65             return [self.get_example(i) for i in index]
     66         else:
---> 67             return self.get_example(index)
     68 
     69     def __len__(self):

/usr/local/lib/python3.6/dist-packages/chainer/datasets/transform_dataset.py in get_example(self, i)
     49 
     50     def get_example(self, i):
---> 51         in_data = self._dataset[i]
     52         return self._transform(in_data)

/usr/local/lib/python3.6/dist-packages/chainer/dataset/dataset_mixin.py in __getitem__(self, index)
     65             return [self.get_example(i) for i in index]
     66         else:
---> 67             return self.get_example(index)
     68 
     69     def __len__(self):

/usr/local/lib/python3.6/dist-packages/chainer/datasets/image_dataset.py in get_example(self, i)
    156 
    157     def get_example(self, i):
--> 158         path, int_label = self._pairs[i]
    159         full_path = os.path.join(self._root, path)
    160         image = _read_image_as_array(full_path, self._dtype)

ValueError: too many values to unpack (expected 2)

該当のソースコード

python
1import chainer.dataset.convert as con
2import os
3import chiner.datasets as ds
4
5def add_labeled_data(folder, all_list):
6  image_files = os.listdir(folder)
7  for i in range(5):
8    for j in range(20):
9      labeled_file = (folder + '{}_{}'.format(i, j))
10      all_list.append(labeled_file)
11  return all_list
12
13def transform64(data):
14  data = data.astype(np.uint8)
15  data = im.fromarray(data.transpose(1, 2, 0))
16  data = data.resize((64, 64), im.BICUBIC)
17  data = np.asarray(data).transpose(2, 0, 1)
18  data = data.astype(np.float32) / 255
19  return data
20
21all_list = []
22add_labeled_data('/content/drive/My Drive/Colab Notebooks/haruna_picture/', all_list)
23add_labeled_data('/content/drive/My Drive/Colab Notebooks/shrek_picture/', all_list)
24dataset = ds.LabeledImageDataset(all_list)
25
26dataset = ds.TransformDataset(dataset, transform64)
27D = len(dataset)
28Dtrain = D // 2
29train,test = ds.split_dataset_random(dataset, Dtrain)
30
31xtrain, ttrain = con.concat_examples(train)
32xtest, ttest = con.concat_examples(train)
33
34