More explicit map printing.

[wuhu]

Map of Compose:

   ~ ( tokenize >> to_tensor >> Batchify(dim=0) >> [..+..] >> cross_entropy_loss )

instead of

<anonymous map>:

   ~ tokenize >> to_tensor >> Batchify(dim=0) >> [..+..] >> cross_entropy_loss

• removes the "anonymous ..."
• adds parentheses around pipelines