*/
  @J2ktIncompatible
  @GwtIncompatible // java.lang.reflect
  @CheckForNull
  private static final Method getStackTraceElementMethod = (jla == null) ? null : getGetMethod();

  /**
   * The "getStackTraceDepth" method, only available on some JDKs so we use reflection to find it
   * when available. When this is null, use the slow way.
   */
  @J2ktIncompatible

It's common that each authentication provider names their flows in a different way, to make it part of their brand.

But in the end, they are implementing the same OAuth2 standard.

///

**FastAPI** includes utilities for all these OAuth2 authentication flows in `fastapi.security.oauth2`.

## `Security` in decorator `dependencies`

@ElementTypesAreNonnullByDefault
final class SingletonImmutableSet<E> extends ImmutableSet<E> {
  // We deliberately avoid caching the asList and hashCode here, to ensure that with
  // compressed oops, a SingletonImmutableSet packs all the way down to the optimal 16 bytes.

  final transient E element;

  SingletonImmutableSet(E element) {
    this.element = Preconditions.checkNotNull(element);
  }

  @Override
  public int size() {
    return 1;

///

```Python hl_lines="1"
{!> ../../docs_src/request_forms_and_files/tutorial001.py!}
```

////

## Define `File` and `Form` parameters

Create file and form parameters the same way you would for `Body` or `Query`:

//// tab | Python 3.9+

```Python hl_lines="10-12"
{!> ../../docs_src/request_forms_and_files/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```

////

This will make `tags` be a list, although it doesn't declare the type of the elements of the list.

## List fields with type parameter

But Python has a specific way to declare lists with internal types, or "type parameters":

### Import typing's `List`

In Python 3.9 and above you can use the standard `list` to declare these type annotations as we'll see below. 💡

        "tax": 3.2
    },
    "user": {
        "username": "dave",
        "full_name": "Dave Grohl"
    }
}
```

/// note

Notice that even though the `item` was declared the same way as before, it is now expected to be inside of the body with a key `item`.

///

**FastAPI** will do the automatic conversion from the request, so that the parameter `item` receives its specific content and the same for `user`.

 * given the content data that was used to create the source or that was written to the sink.
 *
 * <p>A single {@code SourceSinkFactory} implementation generally corresponds to one specific way of
 * creating a source or sink, such as {@link Files#asByteSource(File)}. Implementations of {@code
 * SourceSinkFactory} for common.io are found in {@link SourceSinkFactories}.
 *
 * @param <S> the source or sink type

  }

  @GwtIncompatible // super.subListUnchecked does not exist; inherited subList is valid if slow
  /*
   * TODO(cpovirk): if we start to override indexOf/lastIndexOf under GWT, we'll want some way to
   * override subList to return an ImmutableSortedAsList for better performance. Right now, I'm not
   * sure there's any performance hit from our failure to override subListUnchecked under GWT
   */
  @Override

When you mount a sub-application as described above, FastAPI will take care of communicating the mount path for the sub-application using a mechanism from the ASGI specification called a `root_path`.

That way, the sub-application will know to use that path prefix for the docs UI.

          .url("https://api.github.com/search/repositories?q=http")
          .build();

      OkHttpClient clientForCall;
      if (i == 2) {
        // Force this request's response to be written to the cache. This way, subsequent responses
        // can be read from the cache.
        System.out.println("Force cache: true");
        clientForCall = client.newBuilder()
            .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)