How to use the lineflow.core.DatasetMixin function in lineflow

def test_dunder_iter(self):
        class ImplementedIter(DatasetMixin):
            def __iter__(self):
                return super(ImplementedIter, self).__iter__()

            def get_example(self): ...

            def __len__(self): ...

        d = ImplementedIter()
        self.assertListEqual([], list(d))

def test_dunder_len(self):
        class ImplementedLen(DatasetMixin):
            def __iter__(self): ...

            def get_example(self, i): ...

            def __len__(self):
                return super(ImplementedLen, self).__len__()

        d = ImplementedLen()
        self.assertEqual(len(d), 0)

def test_get_example(self):
        class ImplementedGetExample(DatasetMixin):
            def __iter__(self): ...

            def get_example(self, i):
                return super(ImplementedGetExample, self).get_example(i)

            def __len__(self):
                return 1

        d = ImplementedGetExample()
        with self.assertRaises(IndexError):
            d[0]

def test_acts_list(self):
        self.assertIsInstance([], DatasetMixin)

def test_dunder_subclasshook(self):
        class Dummy(DatasetMixin):
            def __iter__(self): ...

            def get_example(self, i): ...

            def __len__(self): ...
        self.assertEqual(Dummy.__subclasshook__(Dummy),
                         NotImplemented)

def test_acts_tuple(self):
        self.assertIsInstance((), DatasetMixin)

def __len__(self) -> int:
        return 0

    @classmethod
    def __subclasshook__(cls, C):
        if cls is DatasetMixin:
            return _check_methods(C, '__iter__', 'get_example', '__len__')
        return NotImplemented


DatasetMixin.register(Sequence)
DatasetMixin.register(easyfile.TextFile)
DatasetMixin.register(easyfile.CsvFile)


class Dataset(DatasetMixin):
    """Dataset wrapping ``DatasetMixin`` object.

    Args:
        dataset (DatasetMixin): ``Sequence``, ``easyfile.TextFile``, or ``easyfile.CsvFile`` object.
    """

    def __init__(self,
                 dataset: DatasetMixin) -> None:
        assert isinstance(dataset, DatasetMixin)

        self._dataset = dataset
        self._length = None

    def __iter__(self) -> Iterator[Any]:
        yield from self._dataset

raise IndexError

    @abstractmethod
    def __len__(self) -> int:
        return 0

    @classmethod
    def __subclasshook__(cls, C):
        if cls is DatasetMixin:
            return _check_methods(C, '__iter__', 'get_example', '__len__')
        return NotImplemented


DatasetMixin.register(Sequence)
DatasetMixin.register(easyfile.TextFile)
DatasetMixin.register(easyfile.CsvFile)


class Dataset(DatasetMixin):
    """Dataset wrapping ``DatasetMixin`` object.

    Args:
        dataset (DatasetMixin): ``Sequence``, ``easyfile.TextFile``, or ``easyfile.CsvFile`` object.
    """

    def __init__(self,
                 dataset: DatasetMixin) -> None:
        assert isinstance(dataset, DatasetMixin)

        self._dataset = dataset
        self._length = None

def __subclasshook__(cls, C):
        if cls is DatasetMixin:
            return _check_methods(C, '__iter__', 'get_example', '__len__')
        return NotImplemented

def __init__(self, *datasets: List[DatasetMixin]) -> None:
        assert all(isinstance(d, DatasetMixin) for d in datasets)
        self._datasets = datasets
        self._length = None