Return request cookies.

        A read-only dictionary-like object.

def cookies(self) -> Mapping[str, str]:
        """Return request cookies.

        A read-only dictionary-like object.
        """
        raw = self.headers.get(hdrs.COOKIE, '')
        parsed = SimpleCookie(raw)
        return MappingProxyType(
            {key: val.value for key, val in parsed.items()})