def METHOD_NAME(self):
    cmdline = 'ec2 attach-internet-gateway '
    cmdline += '--internet-gateway-id igw-c0a643a9 --vpc-id vpc-a01106 '
    cmdline += '--generate-cli-skeleton output'
    stdout, _, _ = self.assert_params_for_cmd(
        cmdline,
        {'InternetGatewayId': 'igw-c0a643a9', 'VpcId': 'vpc-a01106'})
    # There should be no output as the command has no output shape
    self.assertEqual('', stdout)