def content_type(self) -> str:
        """The value of content part for Content-Type HTTP header."""
        raw = self._headers.get(hdrs.CONTENT_TYPE)  # type: ignore[attr-defined]
        if self._stored_content_type != raw:
            self._parse_content_type(raw)
        return self._content_type  # type: ignore[return-value]
The value of content part for Content-Type HTTP header.
lib/aiohttp/helpers.py