**Note**: You can mix `def` and `async def` in your *path operation functions* as much as you need and define each one using the best option for you. FastAPI will do the right thing with them.

Anyway, in any of the cases above, FastAPI will still work asynchronously and be extremely fast.

But by following the steps above, it will be able to do some performance optimizations.

## Technical Details { #technical-details }

{* ../../docs_src/request_form_models/tutorial002_an_py39.py hl[12] *}

If a client tries to send some extra data, they will receive an **error** response.

For example, if the client tries to send the form fields:

* `username`: `Rick`
* `password`: `Portal Gun`
* `extra`: `Mr. Poopybutthole`

They will receive an error response telling them that the field `extra` is not allowed:

```json
{
    "detail": [
        {

 * {@link DeadEvent} and reposted.
 *
 * <p>If a subscriber for a supertype of all events (such as Object) is registered, no event will
 * ever be considered dead, and no DeadEvents will be generated. Accordingly, while DeadEvent
 * extends {@link Object}, a subscriber registered to receive any Object will never receive a
 * DeadEvent.
 *
 * <p>This class is safe for concurrent use.
 *
 * <p>See the Guava User Guide article on <a

accounts across sites and the ability to disable root accounts eventually.

However, this means that STS tokens signed previously by root credentials will no longer be valid upon upgrading to the latest version with this change. Please re-generate them as you usually do. Additionally, if site replication is ever removed - the STS tokens will become invalid, regenerate them as you usually do....

 * and ignored. Otherwise, they will be re-thrown as {@link CrawlerSystemException}.
 * </p>
 *
 */
public abstract class AbstractIntervalController implements IntervalController {

    /**
     * Indicates whether exceptions during the delay process should be ignored.
     * If set to true, exceptions will be caught and ignored. If set to false,

   * except {@link Object#equals}, {@link Object#hashCode} and {@link Object#toString}. The result
   * will be returned as the proxied method's return value.
   *
   * <p>Unlike {@link #invoke}, {@code args} will never be null. When the method has no parameter,
   * an empty array is passed in.
   */
  protected abstract @Nullable Object handleInvocation(

///

It will:

* Return that status code in the response.
* Document it as such in the OpenAPI schema (and so, in the user interfaces):

<img src="/img/tutorial/response-status-code/image01.png">

/// note

Some response codes (see the next section) indicate that the response does not have a body.

FastAPI knows this, and will produce OpenAPI docs that state there is no response body.

Python will complain if you put a value with a "default" before a value that doesn't have a "default".

But you can re-order them, and have the value without a default (the query parameter `q`) first.

		readerToBuf:   r2b,
		stashBuffer:   b,
	}
}

// Done will release any resources used by the parallelReader.
func (p *parallelReader) Done() {
	if p.stashBuffer != nil {
		globalBytePoolCap.Load().Put(p.stashBuffer)
		p.stashBuffer = nil
	}
}

// preferReaders can mark readers as preferred.
// These will be chosen before others.
func (p *parallelReader) preferReaders(prefer []bool) {

The modules under this directory will be released exactly once each. Once that