def filename(self) -> Optional[str]:
        """Returns filename specified in Content-Disposition header.

        Returns None if the header is missing or malformed.
        """
        _, params = parse_content_disposition(self.headers.get(CONTENT_DISPOSITION))
        return content_disposition_filename(params, "filename")
Returns filename specified in Content-Disposition header.

        Returns None if the header is missing or malformed.
        
lib/aiohttp/multipart.py