refers to definition of API in botocore, and autogenerates function
    You can see example of elbv2 from link below.
      https://github.com/boto/botocore/blob/develop/botocore/data/elbv2/2015-12-01/service-2.json

def get_function_in_models(service, operation):
    """refers to definition of API in botocore, and autogenerates function
    You can see example of elbv2 from link below.
      https://github.com/boto/botocore/blob/develop/botocore/data/elbv2/2015-12-01/service-2.json
    """
    client = boto3.client(service)
    aws_operation_name = to_upper_camel_case(operation)
    op_model = client._service_model.operation_model(aws_operation_name)
    inputs = op_model.input_shape.members
    if not hasattr(op_model.output_shape, 'members'):
        outputs = {}
    else:
        outputs = op_model.output_shape.members
    input_names = [to_snake_case(_) for _ in inputs.keys() if _ not in INPUT_IGNORED_IN_BACKEND]
    output_names = [to_snake_case(_) for _ in outputs.keys() if _ not in OUTPUT_IGNORED_IN_BACKEND]
    if input_names:
        body = 'def {}(self, {}):\n'.format(operation, ', '.join(input_names))
    else:
        body = 'def {}(self)\n'
    body += '    # implement here\n'
    body += '    return {}\n\n'.format(', '.join(output_names))

    return body