And dependencies can be created in a very simple and intuitive way that allows you to just import the Python packages you need, and integrate them with your API functions in a couple of lines of code, *literally*.

# Query Parameters and String Validations { #query-parameters-and-string-validations }

**FastAPI** allows you to declare additional information and validation for your parameters.

Let's take this application as example:

{* ../../docs_src/query_params_str_validations/tutorial001_py310.py hl[7] *}

    ClosingFuture<U> apply(DeferredCloser closer, @ParametricNullness T input) throws Exception;
  }

  /**
   * An object that holds the final result of an asynchronous {@link ClosingFuture} operation and
   * allows the user to close all the closeable objects that were captured during it for later
   * closing.
   *
   * <p>The asynchronous operation will have completed before this object is created.
   *

import org.opentest4j.TestAbortedException

/**
 * Marks a test as Platform aware, before the test runs a consistent Platform will be
 * established e.g. SecurityProvider for Conscrypt installed.
 *
 * Also allows a test file to state general platform assumptions, or for individual test.
 */
@Suppress("unused", "MemberVisibilityCanBePrivate")
open class PlatformRule
  @JvmOverloads
  constructor(

## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

* The interactive API documentation will be automatically updated, including the new body:

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Click on the button "Try it out", it allows you to fill the parameters and directly interact with the API:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

smaller chunks.  A client can specify a limit to the number of results to return, and if more results exist a token will be returned that allows the client to continue the previous list call repeatedly until all results are retrieved.  The resulting list is identical to a list call that does not perform chunking thanks to capabilities provided by etcd3.  This allows the server to use less memory and CPU responding with very large lists.  This feature is gated as APIListChunking and is not enabled by...

 * complete details.
 *
 * @deprecated NTLMv1 only
 */
/**
 * An HTTP servlet filter that provides NTLM authentication support.
 * This filter allows web applications to authenticate users via NTLM/Windows authentication.
 */
@Deprecated
public class NtlmHttpFilter implements Filter {

    /**
     * Default constructor.
     */
    public NtlmHttpFilter() {

    * The pod annotation  `security.alpha.kubernetes.io/unsafe-sysctls` allows customization of namespaced sysctls where isolation is unclear....

- Allow pods to use the `net.ipv4.tcp_rmem` and `net.ipv4.tcp_wmem` sysctl by default
  when the kernel version is 4.15 or higher. With the kernel 4.15 the sysctl became namespaced.