assertEquals(message, exception.getMessage());
        assertNull(exception.getCause());
    }

    @Test
    public void test_constructor_withNestedCause() {
        // Test constructor with nested exceptions
        Throwable rootCause = new IllegalStateException("Root cause");
        Throwable intermediateCause = new RuntimeException("Intermediate cause", rootCause);
        String message = "Top level error";

                            return
                        }
                        val outputPrefix = if (file.startsWith("/META-INF/versions")) {
                            // Java 9 multi-release JAR entry, we must keep it nested in the output
                            file.subpath(0, 3).toString()
                        } else {
                            ""
                        }

It is also built to work as a future reference so you can come back and see exactly what you need.

## Run the code { #run-the-code }

All the code blocks can be copied and used directly (they are actually tested Python files).

To run any of the examples, copy the code to a file `main.py`, and start `fastapi dev`:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev

{* ../../docs_src/dataclasses_/tutorial002_py310.py hl[1,6:12,18] *}

该数据类会被自动转换为 Pydantic 的数据类。

这样，它的模式会显示在 API 文档界面中：

<img src="/img/tutorial/dataclasses/image01.png">

## 在嵌套数据结构中使用数据类 { #dataclasses-in-nested-data-structures }

你也可以把 `dataclasses` 与其它类型注解组合在一起，创建嵌套数据结构。

在某些情况下，你可能仍然需要使用 Pydantic 的 `dataclasses` 版本。例如，如果自动生成的 API 文档出现错误。

在这种情况下，你可以直接把标准的 `dataclasses` 替换为 `pydantic.dataclasses`，它是一个可直接替换的实现：

        assertNotNull(exception.getCause().getStackTrace());
        assertTrue(exception.getCause().getStackTrace().length > 0);
    }

    @Test
    public void test_multiLevelCause() {
        // Test with nested exceptions
        Throwable rootCause = new IllegalStateException("Root problem");
        Throwable intermediateCause = new RuntimeException("Intermediate problem", rootCause);

   */
  protected final <T> void setDistinctValues(Class<T> type, T value1, T value2) {
    tester.setDistinctValues(type, value1, value2);
  }

  /** Specifies that classes that satisfy the given predicate aren't tested for sanity. */
  protected final void ignoreClasses(Predicate<? super Class<?>> condition) {
    this.classFilter = and(this.classFilter, not(condition));
  }

  private static AssertionError sanityError(

	// Composite Index: Flattened structure.
	Data0A string `gorm:"index:,composite:comp_id0"`
	Data0B string `gorm:"index:,composite:comp_id0"`

	// Composite Index: Nested structure.
	Data1A string `gorm:"index:,composite:comp_id1"`
	CompIdxLevel1C

	// Composite Index: Unique and priority.
	Data2A string `gorm:"index:,unique,composite:comp_id2,priority:2"`
	CompIdxLevel2C
}

// information - e.g. the SSE-C key - from the metadata map.
// It has the same semantics as RemoveSensitiveHeaders.
func RemoveSensitiveEntries(metadata map[string]string) { // The functions is tested in TestRemoveSensitiveHeaders for compatibility reasons
	delete(metadata, xhttp.AmzServerSideEncryptionCustomerKey)
	delete(metadata, xhttp.AmzServerSideEncryptionCopyCustomerKey)

    }

    // Tests for atomic file operations (TOCTOU fix)

    @Test
    public void test_createDirectories_nestedPath() throws Exception {
        // Test that Files.createDirectories works correctly for nested paths
        Path tempDir = Files.createTempDirectory("toctou_test");
        try {
            Path nestedPath = tempDir.resolve("level1").resolve("level2").resolve("level3");

	// DisableForeignKeyConstraintWhenMigrating
	DisableForeignKeyConstraintWhenMigrating bool
	// IgnoreRelationshipsWhenMigrating
	IgnoreRelationshipsWhenMigrating bool
	// DisableNestedTransaction disable nested transaction
	DisableNestedTransaction bool
	// AllowGlobalUpdate allow global update
	AllowGlobalUpdate bool
	// QueryFields executes the SQL query with all fields of the table
	QueryFields bool