private Absent() {}

  @Override
  public boolean isPresent() {
    return false;
  }

  @Override
  public T get() {
    throw new IllegalStateException("Optional.get() cannot be called on an absent value");
  }

  @Override
  public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

  @SuppressWarnings("unchecked") // safe covariant cast

            "loc": [
                "path",
                "item_id"
            ],
            "msg": "value is not a valid integer",
            "type": "type_error.integer"
        }
    ]
}

```

被替换为了以下文本格式的错误信息：

```
1 validation error
path -> item_id
  value is not a valid integer (type=type_error.integer)

```

### `RequestValidationError` vs `ValidationError`

			t.Fatal(failTestStr(anonTestStr, "error response bucket name differs from expected value"))
		}

		if actualError.Key != objectName {
			t.Fatal(failTestStr(anonTestStr, "error response object name differs from expected value"))
		}
	}

	// test for unknown auth case.
	anonReq.Body = readerTwo
	// Setting the `Authorization` header to a random value so that the signature falls into unknown auth case.

     * This field indicates when the crawling session should expire or be cleaned up.
     */
    public String expiredTime;

    /**
     * The timestamp when this crawling session was created.
     * Stored as a long value representing milliseconds since epoch.
     */
    @ValidateTypeFailure
    public Long createdTime;

    /**
     * Initializes the form with default null values.

        this.timeout = 0;
    }

    /**
     * Constructs a pipe wait request with timeout.
     *
     * @param name the pipe name to wait for
     * @param timeout the timeout value in milliseconds
     */
    public FsctlPipeWaitRequest(final String name, final long timeout) {
        this.nameBytes = name.getBytes(StandardCharsets.UTF_16LE);
        this.timeoutSpecified = true;

        getNullLocation(),
        find(null));
  }

  public void testFind_wrongType() {
    try {
      assertEquals(
          getMethodName() + "(wrongType) should return -1 or throw", -1, find(WrongType.VALUE));
    } catch (ClassCastException tolerated) {
    }
  }

  }

  public void testContains_wrongType() {
    try {
      assertFalse(
          "contains(wrongType) should return false or throw", collection.contains(WrongType.VALUE));
    } catch (ClassCastException tolerated) {
    }
  }

            return false;
        }

        if (isIgnoredProperty(strValue)) {
            return false;
        }

        // for declaration like @Parameter( property = "config.property" )
        // the value will contain ${config.property}

        try {
            return expressionEvaluator.evaluate(strValue) != null;
        } catch (ExpressionEvaluationException e) {
            // not important

Remember that when you import `Query`, `Path`, and others from `fastapi`, those are actually functions that return special classes.

///

/// tip

Notice how each model's attribute with a type, default value and `Field` has the same structure as a *path operation function's* parameter, with `Field` instead of `Path`, `Query` and `Body`.

///

## Add extra information { #add-extra-information }

     * @return the requests per second value, or null for no limit
     */
    protected String getReindexRequestsPerSecound(final FessConfig fessConfig) {
        if (StringUtil.isBlank(fessConfig.getIndexReindexRequestsPerSecond())) {
            return null;
        }
        final String value = fessConfig.getIndexReindexRequestsPerSecond();
        if ("adaptive".equalsIgnoreCase(value)) {