        The method uses high-performance os.sendfile if available.

        file must be a regular file object opened in binary mode.

        offset tells from where to start reading the file. If specified,
        count is the total number of bytes to transmit as opposed to
        sending the file until EOF is reached. File position is updated on
        return or also in case of error in which case file.tell()
        can be used to figure out the number of bytes
        which were sent.

        fallback set to True makes asyncio to manually read and send
        the file when the platform does not support the sendfile syscall
        (e.g. Windows or SSL socket on Unix).

        Raise SendfileNotAvailableError if the system does not support
        sendfile syscall and fallback is False.
        z