因为使用的是相对 URL，如果 API 位于 `https://example.com/`，则指向 `https://example.com/token`。但如果 API 位于 `https://example.com/api/v1/`，它指向的就是`https://example.com/api/v1/token`。

使用相对 URL 非常重要，可以确保应用在遇到[使用代理](../../advanced/behind-a-proxy.md){.internal-link target=_blank}这样的高级用例时，也能正常运行。

///

该参数不会创建端点或*路径操作*，但会声明客户端用来获取令牌的 URL `/token` 。此信息用于 OpenAPI 及 API 文档。

接下来，学习如何创建实际的路径操作。

/// info | 说明

 */
abstract class EventListener {
  /**
   * Invoked as soon as a call is enqueued or executed by a client. In case of thread or stream
   * limits, this call may be executed well before processing the request is able to begin.
   *
   * This will be invoked only once for a single [Call]. Retries of different routes or redirects
   * will be handled within the boundaries of a single [callStart] and [callEnd]/[callFailed] pair.
   */

  reached or started.

  All of these operations will produce their own unique errors in the absence of
  a coordinated offline strategy. In addition, efforts to unite these failing
  behaviors behind a consistent user interface is much, much more difficult if
  the system can't tell whether it has access to the network required by these
  operations.

pkg crypto, const BLAKE2b_512 Hash
pkg crypto, const BLAKE2s_256 = 16
pkg crypto, const BLAKE2s_256 Hash
pkg crypto/x509, type Certificate struct, ExcludedDNSDomains []string
pkg database/sql, method (*Conn) BeginTx(context.Context, *TxOptions) (*Tx, error)
pkg database/sql, method (*Conn) Close() error
pkg database/sql, method (*Conn) ExecContext(context.Context, string, ...interface{}) (Result, error)

		{"", false},
		{"a", false},
		{"ab", false},
		{".starts-with-a-dot", false},
		{"ends-with-a-dot.", false},
		{"ends-with-a-dash-", false},
		{"-starts-with-a-dash", false},
		{"THIS-BEGINS-WITH-UPPERCASe", false},
		{"tHIS-ENDS-WITH-UPPERCASE", false},
		{"ThisBeginsAndEndsWithUpperCasE", false},
		{"una ñina", false},
		{"dash-.may-not-appear-next-to-dot", false},

			expectedAuthField: signValues{},
			expectedErrCode:   ErrAuthHeaderEmpty,
		},
		// Test case - 2.
		// Test case with no sign v4 Algorithm prefix.
		// A valid authorization string should begin(prefix)
		{
			inputV4AuthStr:    "no-singv4AlgorithmPrefix",
			expectedAuthField: signValues{},
			expectedErrCode:   ErrSignatureVersionNotSupported,
		},
		// Test case - 3.

    }
  }

  /**
   * Removes a number of occurrences of the specified element from this multiset. If the multiset
   * contains fewer than this number of occurrences to begin with, all occurrences will be removed.
   *
   * @param element the element whose occurrences should be removed
   * @param occurrences the number of occurrences of the element to remove

           * go out of date (for a collection like CopyOnWriteArrayList, which may have been safely
           * modified concurrently), or it might have been only an estimate to begin with (for a
           * collection like ConcurrentHashMap, which sums up several counters that may not be in
           * sync with one another). We accommodate that by resizing as necessary.
           */

Esta é uma função Python.

Ela será chamada pelo **FastAPI** sempre que receber uma requisição para a URL "`/`" usando uma operação `GET`.

Neste caso, é uma função `async`.

---

Você também pode defini-la como uma função normal em vez de `async def`:

{* ../../docs_src/first_steps/tutorial003_py39.py hl[7] *}

/// note | Nota

  @Override
  boolean add(@ParametricNullness E element);

  /**
   * Removes a number of occurrences of the specified element from this multiset. If the multiset
   * contains fewer than this number of occurrences to begin with, all occurrences will be removed.
   * Note that if {@code occurrences == 1}, this is functionally equivalent to the call {@code
   * remove(element)}.
   *