### Use cases: external service { #use-cases-external-service }

An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

/// warning

Extra keys passed to `Field` will also be present in the resulting OpenAPI schema for your application.
As these keys may not necessarily be part of the OpenAPI specification, some OpenAPI tools, for example [the OpenAPI validator](https://validator.swagger.io/), may not work with your generated schema.

///

## Recap { #recap }

You can use Pydantic's `Field` to declare extra validations and metadata for model attributes.

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

如果客戶端嘗試在**查詢參數**中發送一些**額外的**資料，他們將會收到一個**錯誤**回應。

例如，如果客戶端嘗試發送一個值為 `plumbus` 的 `tool` 查詢參數，如：

```http
https://example.com/items/?limit=10&tool=plumbus
```

他們將收到一個**錯誤**回應，告訴他們查詢參數 `tool` 是不允許的：

```json
{
    "detail": [
        {
            "type": "extra_forbidden",
            "loc": ["query", "tool"],

#!/usr/bin/env bash
# Copyright 2015 The Go Authors. All rights reserved.
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file.

# When run as (for example)
#
#	GOOS=linux GOARCH=ppc64 bootstrap.bash
#
# this script cross-compiles a toolchain for that GOOS/GOARCH
# combination, leaving the resulting tree in ../../go-${GOOS}-${GOARCH}-bootstrap.
# That tree can be copied to a machine of the given target type

import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.coroutines.executeAsync
import okhttp3.survey.types.SuiteId
import okio.ByteString.Companion.decodeHex
import okio.IOException

/** Example: "0x00,0x08",TLS_RSA_EXPORT_WITH_DES40_CBC_SHA,Y,N,[RFC4346] */
val IANA_CSV_PATTERN = "\"0x(\\w\\w),0x(\\w\\w)\",(\\w+).*".toRegex()

fun parseIanaCsvRow(s: String): SuiteId? {

 * This annotation can be used in conjunction with {@link Inject} to specify
 * which implementation should be injected when multiple candidates exist.
 * The value represents a unique identifier for the dependency.
 * <p>
 * Example usage:
 * <pre>
 * {@literal @}Inject
 * {@literal @}Named("mysql")
 * private Repository mysqlRepository;
 * </pre>
 *
 * @see Inject
 * @see Qualifier
 * @since 4.0.0
 */
@Qualifier

 * through the Java ServiceLoader mechanism and their provided languages will be available
 * throughout the Maven build process.
 * <p>
 * Example usage:
 * <pre>
 * public class CustomLanguageProvider implements LanguageProvider {
 *     public Collection&lt;Language&gt; provides() {
 *         return Collections.singleton(language("kotlin"));
 *     }
 * }

 *
 * <p>The size of the data structure used by ArrayBasedCharEscaper and ArrayBasedUnicodeEscaper is
 * proportional to the highest valued character that has a replacement. For example a replacement
 * map containing the single character '{@literal \}u1000' will require approximately 16K of memory.
 * As such sharing this data structure between escaper instances is the primary goal of this class.
 *

   * mode}.
   *
   * <p>For the case of {@link RoundingMode#HALF_DOWN}, {@code HALF_UP}, and {@code HALF_EVEN},
   * infinite {@code double} values are considered infinitely far away. For example, 2^2000 is not
   * representable as a double, but {@code roundToDouble(BigDecimal.valueOf(2).pow(2000), HALF_UP)}
   * will return {@code Double.MAX_VALUE}, not {@code Double.POSITIVE_INFINITY}.
   *

        assertTrue(tags[0].toString().contains("attrValue=value123"));

        tags = PrunedTag.parse("a[href=https://example.com]");
        assertEquals(1, tags.length);
        assertTrue(tags[0].toString().contains("attrName=href"));
        assertTrue(tags[0].toString().contains("attrValue=https://example.com"));
    }

    public void test_hashCode_consistency() {
        PrunedTag tag1 = new PrunedTag("div");