Dataset cloning wraps the label

[chschroeder]

Bug description

Selecting a sub(data)set and then cloning a dataset wraps the labels in a superfluous "ndarray()". This affects PytorchTextClassificationDataset and TransformersDataset.

Edit:
I noticed this because clf.predict() on the cloned dataset raised TypeError: len() of unsized object.

Steps to reproduce

Example for TransformersDataset:

import unittest
from tests.utils.datasets import random_transformer_dataset


class CloneBugTest(unittest.TestCase):

    def test_asd(self):
        dataset = random_transformer_dataset(num_samples=20,
                                             multi_label=False,
                                             num_classes=3)
        indices = [0, 1]
  
        dataset_cloned = dataset[indices].clone()

        first_label = dataset.data[0][TransformersDataset.INDEX_LABEL]
        first_label_cloned = dataset_cloned.data[0][TransformersDataset.INDEX_LABEL]

        print(first_label, str(first_label), repr(first_label))
        print(first_label_cloned, str(first_label_cloned), repr(first_label_cloned))

Output:

0 0 0
0 0 array(0)

Expected behavior

Expected Output:

0 0 0
0 0 0

Environment:

Python version: 3.8
small-text version: 1.3.0
small-text integrations (e.g., transformers): transformers
PyTorch version (if applicable): -

Installation (pip, conda, or from source): pip
CUDA version (if applicable): -

Additional information

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