def supportsCheckerFactory(self, factory):
        """
        Returns whether a checker factory will provide at least one of
        the credentials interfaces that we care about.
        """
        for interface in factory.credentialInterfaces:
            if self.supportsInterface(interface):
                return True
        return False

        Returns whether a checker factory will provide at least one of
        the credentials interfaces that we care about.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/strcred.py