default:
        return new ImmutableEnumSet<>(set);
    }
  }

  /*
   * Notes on EnumSet and <E extends Enum<E>>:
   *
   * This class isn't an arbitrary ForwardingImmutableSet because we need to
   * know that calling {@code clone()} during deserialization will return an
   * object that no one else has a reference to, allowing us to guarantee
   * immutability. Hence, we support only {@link EnumSet}.
   */

   *       fail.
   *   <li>If the constructor or factory method takes a parameter that {@link
   *       AbstractPackageSanityTests} doesn't know how to construct, the test will fail.
   *   <li>If there is no visible constructor or visible static factory method declared by {@code
   *       C}, {@code C} is skipped for serialization test, even if it implements {@link

## Pydantic { #pydantic }

All the data validation is performed under the hood by [Pydantic](https://docs.pydantic.dev/), so you get all the benefits from it. And you know you are in good hands.

You can use the same type declarations with `str`, `float`, `bool` and many other complex data types.

Several of these are explored in the next chapters of the tutorial.

For that you need to access the request directly.

{* ../../docs_src/using_request_directly/tutorial001_py310.py hl[1,7:8] *}

By declaring a *path operation function* parameter with the type being the `Request` **FastAPI** will know to pass the `Request` in that parameter.

/// tip

Note that in this case, we are declaring a path parameter beside the request parameter.

        // if we know the size and it fits in an int
        if (size.isPresent() && size.get().longValue() == size.get().intValue()) {
          // otherwise try to presize a StringBuilder
          // it is kind of lame that we need to construct a decoder to access this value.
          // if this is a concern we could add special cases for some known charsets (like utf8)

        // if we know the size and it fits in an int
        if (size.isPresent() && size.get().longValue() == size.get().intValue()) {
          // otherwise try to presize a StringBuilder
          // it is kind of lame that we need to construct a decoder to access this value.
          // if this is a concern we could add special cases for some known charsets (like utf8)

Calls are executed in one of two ways:

 * **Synchronous:** your thread blocks until the response is readable.

        for (Platform platform : Platform.values()) {
            for (boolean bundledJdk : new boolean[] { true, false }) {
                // create a new project in each iteration, so that we know we are resolving the only additional project being created
                Project project = createProject(BWC_MINOR);
                String projectName = projectName(platform.toString(), bundledJdk);

#*    *##elseif ( $license.name == "CDDL + GPLv2 with classpath exception" )
#*      *##set ( $spdx = 'CDDL+GPLv2-with-classpath-exception' )
#*    *##else
#*      *### unrecognized license will require analysis to know obligations
#*      *##set ( $spdx = $license )
#*    *##end
#*    *###
#*    *### fix project urls that are wrong in pom
#*    *##if ( $project.url.startsWith( "http://www.eclipse.org/sisu/" ) )

That documentation will show up in the Swagger UI at `/docs` in your API, and it will let external developers know how to build the *external API*.

This example doesn't implement the callback itself (that could be just a line of code), only the documentation part.

/// tip

The actual callback is just an HTTP request.