def acceptableProtocols():
        """
        Returns a list of protocols that can be spoken by the connection
        factory in the form of ALPN tokens, as laid out in the IANA registry
        for ALPN tokens.

        @return: a list of ALPN tokens in order of preference.
        @rtype: L{list} of L{bytes}
        """

        Returns a list of protocols that can be spoken by the connection
        factory in the form of ALPN tokens, as laid out in the IANA registry
        for ALPN tokens.

        @return: a list of ALPN tokens in order of preference.
        @rtype: L{list} of L{bytes}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/interfaces.py