.BadGzipFile: ClassType
.BadGzipFile <: OSError

.GzipFile!: ClassType
.GzipFile! <: File!
.GzipFile!.
    mode: Str
    mtime: Float
    name: Str
    __call__: (
        filename: PathLike,
        mode := Str,
        compresslevel := Nat,
        fileobj := FileLike,
        mtime := Float,
    ) -> GzipFile!
    peek: (self: Ref(GzipFile!), n: Nat) -> Bytes

.open!: (
    filename: PathLike,
    mode := Str,
    compresslevel := Nat,
    encoding := Str,
    errors := Str,
    newline := Str,
) => GzipFile!
.compress!: (
    data: Bytes or ByteArray!,
    compresslevel := Nat,
    mtime := Float,
) => Bytes
.decompress!: (
    data: Bytes or ByteArray!,
    mtime := Float,
) => Bytes