@Override
    protected List<GeneratorTask> createTasks() throws Exception {
        info("Emitting Base Service Exception class");
        final String baseClassName = model.getSdkModeledExceptionBaseClassName();
        return Collections.singletonList(
                new FreemarkerGeneratorTask(modelClassDir,
                                            baseClassName,
                                            freemarker.getBaseExceptionClassTemplate(),
                                            ImmutableMapParameter.of(
                                                    "fileHeader", model.getFileHeader(),
                                                    "className", baseClassName,
                                                    "metadata", model.getMetadata(),
                                                    "baseExceptionFqcn", model.getServiceBaseExceptionFqcn())));
    }
If a custom base class is provided we assume it already exists and does not need to be generated
aws-java-sdk-code-generator/src/main/java/com/amazonaws/codegen/emitters/tasks/BaseExceptionClassGeneratorTasks.java