> Modern versions of Python have support for **"asynchronous code"** using something called **"coroutines"**, with **`async` and `await`** syntax.

That should make more sense now. ✨

All that is what powers FastAPI (through Starlette) and what makes it have such an impressive performance.

## Very Technical Details { #very-technical-details }

/// warning

You can probably skip this.

   *   <li>Otherwise, return an instance of {@link ClusterException} that wraps the first exception
   *       in the {@code exceptions} collection.
   * </ul>
   *
   * <p>Though this method takes any {@link Collection}, it often makes most sense to pass a {@link
   * java.util.List} or some other collection that preserves the order in which the exceptions got
   * added.
   *
   * @throws NullPointerException if {@code exceptions} is null

	queryValue := url.Values{}
	queryValue.Set("uploads", "")
	queryValue.Set("prefix", prefix)
	queryValue.Set("delimiter", delimiter)
	queryValue.Set("key-marker", keyMarker)
	queryValue.Set("upload-id-marker", uploadIDMarker)
	queryValue.Set("max-uploads", maxUploads)
	return makeTestTargetURL(endPoint, bucketName, "", queryValue)
}

// return URL for a listing parts on a given upload id.

```
.
├── app                  # "app" is a Python package
│   ├── __init__.py      # this file makes "app" a "Python package"
│   ├── main.py          # "main" module, e.g. import app.main
│   ├── dependencies.py  # "dependencies" module, e.g. import app.dependencies
│   └── routers          # "routers" is a "Python subpackage"
│   │   ├── __init__.py  # makes "routers" a "Python subpackage"

        ? SortedSetTestSuiteBuilder.using((TestSortedSetGenerator<K>) keySetGenerator)
        : SetTestSuiteBuilder.using(keySetGenerator);
  }

  /**
   * To avoid infinite recursion, test suites with these marker features won't have derived suites
   * created for them.
   */
  enum NoRecurse implements Feature<@Nullable Void> {
    SUBMAP,
    DESCENDING;

    @Override

   * Visited Nodes = {N1, N2, N3, N4}
   * </pre>
   */
  private static final class Undirected<N> extends EndpointPairIterator<N> {
    // It's a little weird that we add `null` to this set, but it makes for slightly simpler code.
    private @Nullable Set<@Nullable N> visitedNodes;

    private Undirected(BaseGraph<N> graph) {
      super(graph);

          latch2.countDown()
        }
      }
    val request2Listener: EventListener =
      object : EventListener() {
        override fun connectStart(
          call: Call,
          inetSocketAddress: InetSocketAddress,
          proxy: Proxy,
        ) {
          // Let request1 proceed to make a connection.
          latch1.countDown()

        } else {
          continue; // delete this entry; we already copied an earlier one for the same key
        }
      }
      newEntries[out++] = entry;
    }
    return newEntries;
  }

  /** Makes an entry usable internally by a new ImmutableMap without rereading its contents. */
  static <K, V> ImmutableMapEntry<K, V> makeImmutable(Entry<K, V> entry, K key, V value) {
    boolean reusable =

You will see examples of this in the next chapters, about relational and NoSQL databases, security, etc.

## **FastAPI** compatibility { #fastapi-compatibility }

The simplicity of the dependency injection system makes **FastAPI** compatible with:

* all the relational databases
* NoSQL databases
* external packages
* external APIs
* authentication and authorization systems
* API usage monitoring systems

## OpenAPI { #openapi }

OpenAPI (previously known as Swagger) is the open specification for building APIs (now part of the Linux Foundation).

**FastAPI** is based on **OpenAPI**.

That's what makes it possible to have multiple automatic interactive documentation interfaces, code generation, etc.

OpenAPI has a way to define multiple security "schemes".