assert response.json() == "foo"
    assert response.headers["content-type"] == "application/x-level-1"
    assert "x-level0" in response.headers
    assert "x-level1" in response.headers
    assert "x-level2" not in response.headers
    assert "x-level3" not in response.headers
    assert "x-level4" not in response.headers
    assert "x-level5" not in response.headers


def test_level1_default():

[<a href="#Go_1.18">Go 1.18</a>].
</p>

<pre>
type Reader interface {
	Read(p []byte) (n int, err error)
	Close() error
}

type Writer interface {
	Write(p []byte) (n int, err error)
	Close() error
}

// ReadWriter's methods are Read, Write, and Close.
type ReadWriter interface {
	Reader  // includes methods of Reader in ReadWriter's method set

pkg html/template, func ParseFS(fs.FS, ...string) (*Template, error)
pkg html/template, method (*Template) ParseFS(fs.FS, ...string) (*Template, error)
pkg io, func NopCloser(Reader) ReadCloser
pkg io, func ReadAll(Reader) ([]uint8, error)
pkg io, type ReadSeekCloser interface { Close, Read, Seek }
pkg io, type ReadSeekCloser interface, Close() error
pkg io, type ReadSeekCloser interface, Read([]uint8) (int, error)

pkg net/http, const StatusEarlyHints = 103
pkg net/http, const StatusEarlyHints ideal-int
pkg net/http, func NewRequestWithContext(context.Context, string, string, io.Reader) (*Request, error)
pkg net/http, method (Header) Clone() Header
pkg net/http, method (*Request) Clone(context.Context) *Request
pkg net/http, method (*Transport) Clone() *Transport