def _addCACertsToContext(context):
        """
        Add certificate-authority certificates to an SSL context whose
        connections should trust those authorities.

        @param context: An SSL context for a connection which should be
            verified by some certificate authority.
        @type context: L{OpenSSL.SSL.Context}

        @return: L{None}
        """

        Add certificate-authority certificates to an SSL context whose
        connections should trust those authorities.

        @param context: An SSL context for a connection which should be
            verified by some certificate authority.
        @type context: L{OpenSSL.SSL.Context}

        @return: L{None}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/_sslverify.py