# Header Parameter Models

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

## Header Parameters with a Pydantic Model

  }

  private void assertCleared() {
    assertEquals(0, multimap().size());
    assertEmpty(multimap());
    assertEquals(multimap(), getSubjectGenerator().create());
    assertEmpty(multimap().entries());
    assertEmpty(multimap().asMap());
    assertEmpty(multimap().keySet());
    assertEmpty(multimap().keys());
    assertEmpty(multimap().values());

    Map<String, String> requestBody = new LinkedHashMap<>();
    requestBody.put("longUrl", "https://publicobject.com/2014/12/04/html-formatting-javadocs/");
    RequestBody jsonRequestBody = RequestBody.create(
        mapJsonAdapter.toJson(requestBody), MEDIA_TYPE_JSON);
    Request request = new Request.Builder()
        .url("https://www.googleapis.com/urlshortener/v1/url?key=" + GOOGLE_API_KEY)
        .post(jsonRequestBody)

  public void testEquals_containingNull() {
    ArrayList<E> elements = new ArrayList<>(getSampleElements());
    elements.set(elements.size() / 2, null);
    collection = getSubjectGenerator().create(elements.toArray());
    List<E> other = new ArrayList<>(getSampleElements());
    assertFalse(
        "Two Lists should not be equal if exactly one of them has null at a given index.",
        getList().equals(other));
  }

			tcfg, _, _ := globalBucketMetadataSys.GetTaggingConfig(bucket.Name)

			acctInfo.Buckets = append(acctInfo.Buckets, madmin.BucketAccessInfo{
				Name:                    bucket.Name,
				Created:                 bucket.Created,
				Size:                    size,
				Objects:                 objectsCount,
				ObjectSizesHistogram:    objectsHist,
				ObjectVersionsHistogram: versionsHist,

          (sink.finished || sink.closed) &&
          hasResponseHeaders
        ) {
          return false
        }
        return true
      }
    }

  /** Returns true if this stream was created by this peer. */
  val isLocallyInitiated: Boolean
    get() {
      val streamIsClient = (id and 1) == 1
      return connection.client == streamIsClient
    }

  /**

 *   <li>file system errors: permissions</li>
 * </ul>
 *
 * TODO carlos: all these possible has*Exceptions and get*Exceptions methods make the clients too
 *       complex requiring a long list of checks, need to create a parent/interface/encapsulation
 *       for the types of exceptions
 */
@Deprecated
public class ArtifactResolutionResult {
    private static final String LS = System.lineSeparator();

Then, when you type that username and password, the browser sends them in the header automatically.

## Simple HTTP Basic Auth

* Import `HTTPBasic` and `HTTPBasicCredentials`.
* Create a "`security` scheme" using `HTTPBasic`.
* Use that `security` with a dependency in your *path operation*.
* It returns an object of type `HTTPBasicCredentials`:
    * It contains the `username` and `password` sent.

## Use `CORSMiddleware`

You can configure it in your **FastAPI** application using the `CORSMiddleware`.

* Import `CORSMiddleware`.
* Create a list of allowed origins (as strings).
* Add it as a "middleware" to your **FastAPI** application.

You can also specify whether your backend allows:

* Credentials (Authorization headers, Cookies, etc).

// Should only be called if a failure occurred.
func (o listPathOptions) checkMetacacheState(ctx context.Context, rpc *peerRESTClient) error {
	// We operate on a copy...
	o.Create = false
	c, err := rpc.GetMetacacheListing(ctx, o)
	if err != nil {
		return err
	}
	cache := *c

	if cache.status == scanStateNone || cache.fileNotFound {
		return errFileNotFound
	}