AWS supports the following Ruby runtimes:

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Name | Identifier | SDK for Ruby | Operating system
-- | -- | -- | --
Ruby 2.7 | ruby2.7 | 3.0.1 | Amazon Linux 2
Ruby 2.5 | ruby2.5 | 3.0.1 | Amazon Linux

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Currently, `localstack/lambda` only contains the `ruby2.5` tag. Will the 2.7 runtime be supported in the (near) future?
resource_lambda_name = '{}-{}'.format(TEST_LAMBDA_FUNCTION_PREFIX, short_uid())
        state_machine_name = 'state-machine-{}'.format(short_uid())
        testutil.create_lambda_function(handler_file=TEST_LAMBDA_START_EXECUTION_FILE,
                                        func_name=function_name,
                                        runtime=LAMBDA_RUNTIME_PYTHON36)
        testutil.create_lambda_function(handler_file=TEST_LAMBDA_ECHO_FILE,
                                        func_name=resource_lambda_name,
                                        runtime=LAMBDA_RUNTIME_PYTHON36)
        state_machine_def = {
            'StartAt': 'step1',
            'States': {
                'step1': {
                    'Type': 'Task',
                    'Resource': aws_stack.lambda_function_arn(resource_lambda_name),
                    'ResultPath': '$.result_value',
                    'End': True
                }
            }
        }
        sfn_client = aws_stack.connect_to_service('stepfunctions')
        rs = sfn_client.create_state_machine(
            name=state_machine_name,
            definition=json.dumps(state_machine_def),
            roleArn=aws_stack.role_arn('sfn_role')
        )
        sm_arn = rs['stateMachineArn']
        self.lambda_client.invoke(
            FunctionName=function_name,
            Payload=json.dumps({
                'state_machine_arn': sm_arn,