How to use the skorch.dataset.Dataset function in skorch

def my_train_split(ds, y):
    # Return (corpus.train, corpus.valid) in case the network
    # is fitted using net.fit(corpus.train).
    return ds, skorch.dataset.Dataset(corpus.valid[:200], y=None)

def my_train_split(ds, y):
    return ds, skorch.dataset.Dataset(corpus.valid[:200], y=None)

def uses_placeholder_y(ds):
    """If ``ds`` is a ``skorch.dataset.Dataset`` or a
    ``skorch.dataset.Dataset`` nested inside a
    ``torch.utils.data.Subset`` and uses
    y as a placeholder, return ``True``."""

    if isinstance(ds, torch.utils.data.Subset):
        return uses_placeholder_y(ds.dataset)
    return isinstance(ds, Dataset) and hasattr(ds, "y") and ds.y is None

def is_skorch_dataset(ds):
    """Checks if the supplied dataset is an instance of
    ``skorch.dataset.Dataset`` even when it is nested inside
    ``torch.util.data.Subset``."""
    from skorch.dataset import Dataset
    if isinstance(ds, Subset):
        return is_skorch_dataset(ds.dataset)
    return isinstance(ds, Dataset)