{[]string{}, "", 0, false},

		{str1, "foo", 0, true},
		{str1, "bar", 0, false},
		{str1, "zx", 1, false},

		{str2, "aa", 0, false},
		{str2, "ab", 0, true},
		{str2, "ad", 1, false},
		{str2, "ca", 1, true},
		{str2, "ra", 2, false},

		{str3, "bb", 0, false},
		{str3, "mo", 0, true},
		{str3, "nb", 1, false},
		{str3, "qo", 1, true},
		{str3, "tr", 2, false},
		{str3, "vo", 2, true},

            }
            String str1 = request.getClassifier();
            String classifier = str1 != null && !str1.isEmpty()
                    ? request.getClassifier()
                    : type != null ? type.getClassifier() : "";
            String str = request.getExtension();
            String extension =

        }
        String str1 = request.getClassifier();
        String classifier =
                str1 != null && !str1.isEmpty() ? request.getClassifier() : type != null ? type.getClassifier() : null;
        String str = request.getExtension();
        String extension =
                str != null && !str.isEmpty() ? request.getExtension() : type != null ? type.getExtension() : null;

}

// WritableFile that simply concats into string.
class StringWritableFile : public WritableFile {
 public:
  explicit StringWritableFile(string* str) : str_(*str) {}

  Status Append(StringPiece data) override {
    absl::StrAppend(&str_, data);
    return absl::OkStatus();
  }

  Status Close() override { return absl::OkStatus(); }

  Status Flush() override { return absl::OkStatus(); }

	}

	// Look for the expected things in the coverage profile.
	contents, err := os.ReadFile(textfile)
	strc := string(contents)
	if err != nil {
		t.Fatalf("problems reading text file %s: %v", textfile, err)
	}
	if !strings.Contains(strc, token) {
		t.Logf("content: %s\n", string(contents))
		t.Fatalf("cov profile does not contain aux meta content %q", token)
	}

```

由于我们必须用 `Query(default=None)` 替换默认值 `None`，`Query` 的第一个参数同样也是用于定义默认值。

所以：

```Python
q: Union[str, None] = Query(default=None)
```

...使得参数可选，等同于：

```Python
q: str = None
```

但是 `Query` 显式地将其声明为查询参数。

然后，我们可以将更多的参数传递给 `Query`。在本例中，适用于字符串的 `max_length` 参数：

```Python
q: Union[str, None] = Query(default=None, max_length=50)
```

将会校验数据，在数据无效时展示清晰的错误信息，并在 OpenAPI 模式的*路径操作*中记录该参​​数。

	s := Collect(testSeq)
	want := testSeqResult
	if !Equal(s, want) {
		t.Errorf("got %v, want %v", s, want)
	}
}

var iterTests = [][]string{
	nil,
	{"a"},
	{"a", "b"},
	{"b", "a"},
	strs[:],
}

func TestValuesAppendSeq(t *testing.T) {
	for _, prefix := range iterTests {
		for _, s := range iterTests {
			got := AppendSeq(prefix, Values(s))
			want := append(prefix, s...)

// problematic types such as pointers. Note that it only does special handling
// for the troublesome types used in the test cases; it is not a general
// printer.
func sprintKey(key reflect.Value) string {
	switch str := key.Type().String(); str {
	case "*int":
		ptr := key.Interface().(*int)
		for i := range ints {
			if ptr == &ints[i] {
				return fmt.Sprintf("PTR%d", i)
			}
		}
		return "PTR???"
	case "unsafe.Pointer":