│   ├── dependencies.py
│   └── routers
│   │   ├── __init__.py
│   │   ├── items.py
│   │   └── users.py
│   └── internal
│       ├── __init__.py
│       └── admin.py
```

/// tip

There are several `__init__.py` files: one in each directory or subdirectory.

This is what allows importing code from one file into another.

For example, in `app/main.py` you could have a line like:

```
from app.routers import items

 *
 * {@snippet :
 * public class MyServer implements Closeable {
 *   private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();
 *   // You might also share this between several objects.
 *
 *   private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();
 *   // This ensures that the FinalizablePhantomReference itself is not garbage-collected.
 *

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

        // to specify the absolute path to these files in a customized components.xml
        // file. Ideally, we'd do full pattern-evaluation against the sysprops, but this
        // is a first step. There are several replacements below, in order to normalize
        // the path character before we operate on the string as a regex input, and
        // in order to avoid surprises with the File construction...

 *       example {@link #anyMatch})
 *   <li>conversion methods which copy the {@code FluentIterable}'s contents into a new collection
 *       or array (for example {@link #toList})
 * </ul>
 *
 * <p>Several lesser-used features are currently available only as static methods on the {@link
 * Iterables} class.
 *
 * <p><a id="streams"></a>
 *
 * <h3>Comparison to streams</h3>
 *

 *       example {@link #anyMatch})
 *   <li>conversion methods which copy the {@code FluentIterable}'s contents into a new collection
 *       or array (for example {@link #toList})
 * </ul>
 *
 * <p>Several lesser-used features are currently available only as static methods on the {@link
 * Iterables} class.
 *
 * <p><a id="streams"></a>
 *
 * <h3>Comparison to streams</h3>
 *

/// note | Technical Details

You could also use `from starlette.middleware.cors import CORSMiddleware`.

**FastAPI** provides several middlewares in `fastapi.middleware` just as a convenience for you, the developer. But most of the available middlewares come directly from Starlette.

We utilize nullness annotations in Java code and somewhat rely on IDE warnings to guide us.
However, the Java code we have is not fully annotated, which causes several consequences:
* IDE warnings can be misleading
* Redundant null checks may increase binary size, hurt performance, and increase cognitive load for readers
* Missing null checks may cause NullPointerException

- Provides a set of APIs and services for use from outside the module.
- Has a private implementation.
- Is owned by a single team. A team may own multiple architecture modules.

The modules are arranged into several different "Gradle platforms".
A Gradle platform is a logical distribution that provides support for a specific kind of automation.

   */
  @SuppressWarnings("unchecked")
  public static <T extends @Nullable Object> Collector<T, ?, T> onlyElement() {
    return (Collector) ONLY_ELEMENT;
  }

  /**
   * This atrocity is here to let us report several of the elements in the stream if there were more
   * than one, not just two.
   */
  @SuppressWarnings("EmptyList") // ImmutableList doesn't support nullable element types