`target_col` not used in `to_seq2seq_dataset` in Chapter 15.

The code for `to_seq2seq_dataset` is this
```python
def to_seq2seq_dataset(series, seq_length=56, ahead=14, target_col=1,
batch_size=32, shuffle=False, seed=None):
ds = to_windows(tf.data.Dataset.from_tensor_slices(series), ahead + 1)
ds = to_windows(ds, seq_length).map(lambda S: (S[:, 0], S[:, 1:, 1]))
if shuffle:
ds = ds.shuffle(8 * batch_size, seed=seed)
return ds.batch(batch_size)
```

but this doesn't seem to use the value of `target_col`. Should it not be

```python
ds = to_windows(ds, seq_length).map(lambda S: (S[:, 0], S[:, 1:, target_col]))
```
on the second line?