O `Union` em `Union[str, None]` não é usado pelo FastAPI, mas permitirá que seu editor lhe dê um melhor suporte e detecte erros.

///

## Validação adicional

Nós iremos forçar que mesmo o parâmetro `q` seja opcional, sempre que informado, **seu tamanho não exceda 50 caracteres**.

### Importe `Query`

Para isso, primeiro importe `Query` de `fastapi`:

        }

        int startedCrawlerNum = 0;
        int activeCrawlerNum = 0;
        while (startedCrawlerNum < dataCrawlingThreadList.size()) {
            // Force to stop crawl
            if (systemHelper.isForceStop()) {
                for (final DataCrawlingThread crawlerThread : dataCrawlingThreadList) {
                    crawlerThread.stopCrawling();
                }

 *
 * <p>Disadvantages of EventBus include:
 *
 * <ul>
 *   <li>It makes the cross-references between producer and subscriber harder to find. This can
 *       complicate debugging, lead to unintentional reentrant calls, and force apps to eagerly
 *       initialize all possible subscribers at startup time.
 *   <li>It uses reflection in ways that break when code is processed by optimizers/minimizers like

        assertTrue(result >= 8);
        assertNotNull(response.getResults());
    }

    @Test
    @DisplayName("Test readBytesWireFormat with properly formed empty response")
    void testReadBytesWireFormatProperlyFormedEmpty() throws Exception {
        response = new Smb2QueryDirectoryResponse(mockConfig, Smb2QueryDirectoryRequest.FILE_BOTH_DIRECTORY_INFO);

     * were added by default.
     */
    public fun clearHeaders(): Builder =
      apply {
        headers_ = Headers.Builder()
      }

    /**
     * Adds [header] as an HTTP header. For well-formed HTTP [header] should contain a name followed
     * by a colon and a value.
     */
    public fun addHeader(header: String): Builder =
      apply {
        headers_.add(header)
      }

    /**

{* ../../docs_src/query_params_str_validations/tutorial006_an_py39.py hl[9] *}

### Required, can be `None` { #required-can-be-none }

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but simply do not declare a default value:

	CALL (AX)(PC*1)                 // ERROR "invalid instruction"
	CALL (AX)(SB*1)                 // ERROR "invalid instruction"
	CALL (AX)(FP*1)                 // ERROR "invalid instruction"
	// Forbid memory operands for MOV CR/DR. See #24981.
	MOVQ CR0, (AX)                  // ERROR "invalid instruction"
	MOVQ CR2, (AX)                  // ERROR "invalid instruction"

   * one from the pool. We must take the pooled connection because by taking it from the pool, we've
   * fully acquired it.
   *
   * This test yields threads to force the decision of plan1 to be deliberate and not lucky. In
   * particular, we set up this sequence of events:
   *
   *  1. take plan 0
   *  3. plan 0 connects
   *  4. finish taking plan 1
   *

C'est pourquoi il est logique d'utiliser du code asynchrone ⏸🔀⏯ pour des APIs web.

Ce type d'asynchronicité est ce qui a rendu NodeJS populaire (bien que NodeJS ne soit pas parallèle) et c'est la force du Go en tant que langage de programmation.

Et c'est le même niveau de performance que celui obtenu avec **FastAPI**.

 *
 *  * **Exactly one subdomain**: Use a single asterisk like `*.publicobject.com` to match exactly
 *    one prefix (`www.publicobject.com`, `api.publicobject.com`). Be careful with this approach as
 *    no pinning will be enforced if additional prefixes are present, or if no prefixes are present.
 *
 * Note that any other form is unsupported. You may not use asterisks in any position other than
 * the leftmost label.
 *