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

## Forbid Extra Headers { #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:

{* ../../docs_src/header_param_models/tutorial002_an_py310.py hl[10] *}

//
//go:build linux

package bytes_test

import (
	. "bytes"
	"syscall"
	"testing"
)

// This file tests the situation where byte operations are checking
// data very near to a page boundary. We want to make sure those
// operations do not read across the boundary and cause a page
// fault where they shouldn't.

// These tests run only on linux. The code being tested is

///

## Forbid Extra Cookies { #forbid-extra-cookies }

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

     * and then a list is built. These exceptions are usually thrown in "fatal" cases (and usually prevent Maven
     * from starting), and these exceptions may end up very early on output.
     *
     * @param message the base message to enhance
     * @param problems the collection of problems to include in the message
     * @return a formatted message including details of all problems
     */

 *
 * Build up a collection by starting with [EmptyTags] and repeatedly calling [plus]. Each such call
 * returns a new instance.
 *
 * This collection is optimized for safe concurrent access over a very small number of elements.
 *
 * This collection and is expected to hold fewer than 10 elements. Each operation is _O(N)_, and so
 * building an instance with _N_ elements is _O(N**2)_.
 */
internal sealed class Tags {

   */
  static class ExpensiveComputation implements Function<Integer, BigInteger> {
    @Override
    public BigInteger apply(Integer from) {
      BigInteger v = BigInteger.valueOf(from);
      // Math.sin is very slow for values outside 4*pi
      // Need to take absolute value to avoid inverting the value.
      for (double i = 0; i < 100; i += 20) {
        v =
            v.add(
                v.multiply(

   */
  static class ExpensiveComputation implements Function<Integer, BigInteger> {
    @Override
    public BigInteger apply(Integer from) {
      BigInteger v = BigInteger.valueOf(from);
      // Math.sin is very slow for values outside 4*pi
      // Need to take absolute value to avoid inverting the value.
      for (double i = 0; i < 100; i += 20) {
        v =
            v.add(
                v.multiply(

    attributes:
      label: "What did you see happen?"
      description: Command invocations and their associated output, functions with their arguments and return results, full stacktraces for panics (upload a file if it is very long), etc. Prefer copying text output over using screenshots.
    validations:
      required: true

  - type: textarea
    id: expected-behavior
    attributes:
      label: "What did you expect to see?"

	if err != nil {
		return err
	}
	x.ClientConversation = x.NewConversation()
	return nil
}

// Step takes a string provided from a server (or just an empty string for the
// very first conversation step) and attempts to move the authentication
// conversation forward.  It returns a string to be sent to the server or an
// error if the server message is invalid.  Calling Step after a conversation

    /*
     * We use `fromNullable` instead of `of` because `WeakReference.get()` has a nullable return
     * type.
     *
     * In practice, we are very unlikely to see `null`: The `WeakReference` to the enum constant
     * won't be cleared as long as the enum constant is referenced somewhere, and the enum constant