def opt_help_auth_type(self, authType):
        """
        Show help for a particular authentication type.
        """
        try:
            cf = findCheckerFactory(authType)
        except InvalidAuthType:
            raise usage.UsageError("Invalid auth type: %s" % authType)
        self.authOutput.write("Usage: --auth %s[:ArgString]\n" % authType)
        self.authOutput.write("ArgString format: %s\n" % cf.argStringFormat)
        self.authOutput.write('\n')
        for line in cf.authHelp.strip().splitlines():
            self.authOutput.write('  %s\n' % line.rstrip())
        self.authOutput.write('\n')
        if not self.supportsCheckerFactory(cf):
            self.authOutput.write('  %s\n' % notSupportedWarning)
            self.authOutput.write('\n')
        raise SystemExit(0)

        Show help for a particular authentication type.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/strcred.py