FastAPI生成的OpenAPI规范是否合规？openapi-generator报错排查

我不确定问题出在哪里——FastAPI生成的OpenAPI文件我认为是有效的，但最新版本的openapi-generator-cli判定该文件无效。报错信息如下：

Exception in thread "main" org.openapitools.codegen.SpecValidationException: There were issues with the specification. The option can be disabled via validateSpec (Maven/Gradle) or --skip-validate-spec (CLI).
 | Error count: 1, Warning count: 2
Errors: 
        -attribute paths.'/units/{id}/charts/'(get).parameters.[group_mode].schemas.required is not of type `array`
Warnings: 
        -attribute paths.'/units/{id}/charts/'(get).parameters.[group_mode].schemas.required is not of type `array`

        at org.openapitools.codegen.config.CodegenConfigurator.toContext(CodegenConfigurator.java:701)
        at org.openapitools.codegen.config.CodegenConfigurator.toClientOptInput(CodegenConfigurator.java:728)
        at org.openapitools.codegen.cmd.Generate.execute(Generate.java:519)
        at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
        at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)

对应的OpenAPI参数结构显示：group_mode参数的schemas字段下存在required属性，其值为布尔类型true。

我编写的FastAPI代码如下：

group_mode: GroupMode = Query(
        default="1d",
        description="Group by a parameter. Options are Minute, Hour, Day, Week, Month, Year.",
        required=True,
    ),

想请教问题根源：

• 是OpenAPI规范有效但代码生成器配置错误？
• 还是代码生成器判定正确而FastAPI生成的规范有误？
• 或是我的代码存在问题？

内容的提问来源于stack exchange，提问作者creyD