switch (form.crudMode) {
        case CrudMode.CREATE:
            return OptionalEntity.of(new DataConfig()).map(entity -> {
                entity.setCreatedBy(username);
                entity.setCreatedTime(currentTime);
                return entity;
            });
        case CrudMode.EDIT:
            if (form instanceof EditForm) {

   * @return the number of characters copied
   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue
  public static long copy(Readable from, Appendable to) throws IOException {
    // The most common case is that from is a Reader (like InputStreamReader or StringReader) so
    // take advantage of that.
    if (from instanceof Reader) {
      // optimize for common output types which are optimized to deal with char[]

  /** Adds the given pair of values to the dataset. */
  public void add(double x, double y) {
    // We extend the recursive expression for the one-variable case at Art of Computer Programming
    // vol. 2, Knuth, 4.2.2, (16) to the two-variable case. We have two value series x_i and y_i.
    // We define the arithmetic means X_n = 1/n \sum_{i=1}^n x_i, and Y_n = 1/n \sum_{i=1}^n y_i.

# Extending OpenAPI

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

  /**
   * Returns the data to expect the source or sink to contain given the data that was used to create
   * the source or written to the sink. Typically, this will just return the input directly, but in
   * some cases it may alter the input. For example, if the factory returns a sliced view of a
   * source created with some given bytes, this method would return a subsequence of the given
   * (byte[]) data.
   */
  T getExpected(T data);

        switch (form.crudMode) {
        case CrudMode.CREATE:
            return OptionalEntity.of(new RelatedQuery()).map(entity -> {
                entity.setCreatedBy(username);
                entity.setCreatedTime(currentTime);
                return entity;
            });
        case CrudMode.EDIT:
            if (form instanceof EditForm) {

You can see the required headers in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers

In some special use cases (probably not very common), you might want to **restrict** the headers that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

//// tab | Python 3.10+

	for _, obs := range observations {
		// Send observations once every 1ms, to simulate delay between
		// observations. This is to test the channel based
		// synchronization used internally.
		select {
		case <-ticker.C:
			ttfbHist.With(prometheus.Labels{"api": obs.label}).Observe(obs.val)
		}
	}

	metrics := getHistogramMetrics(ttfbHist, getBucketTTFBDistributionMD(), false)

	if err := windows.GetVolumePathName(wpath, &wvolume[0], uint32(len(wvolume))); err != nil {
		mountPointCache.Store(path, false)
		return false
	}

	switch windows.GetDriveType(&wvolume[0]) {
	case windows.DRIVE_FIXED, windows.DRIVE_REMOVABLE, windows.DRIVE_REMOTE, windows.DRIVE_RAMDISK:
		// Recognize "fixed", "removable", "remote" and "ramdisk" drives as proper drives

     *
     * @param key
     * @return InputLocation
     */
    public InputLocation getLocation(Object key) {
        if (key instanceof String) {
            switch ((String) key) {
                case "": {
                    return this.location;
                }
                default: {
                    return getOtherLocation(key);
                }
            }
        } else {