*   Added a new boolean argument `allow_fast_lookup` to `tf.nn.embedding_lookup_sparse` and `tf.nn.safe_embedding_lookup_sparse`, which enables a simplified and typically faster lookup procedure.

*   `tf.data`

    *   `tf.data.Dataset.zip` now supports Python-style zipping, i.e. `Dataset.zip(a, b, c)`.

A seção:

```Python
from .routers import items, users
```

significa:

* Começando no mesmo pacote em que este módulo (o arquivo `app/main.py`) reside (o diretório `app/`)...
* procure o subpacote `routers` (o diretório em `app/routers/`)...
* e dele, importe o submódulo `items` (o arquivo em `app/routers/items.py`) e `users` (o arquivo em `app/routers/users.py`)...

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