许多Django Rest框架的序列化生成序列化关系的非etype实例

I'm quite new on Django Rest Framework, and I've been trying to write a serializer for one of my models. For my project I intend to output the json result according to the JSON API Standards, and, for doing so, I am using the SerializerMethodField in which I call the method I'm quite new on Django Rest Framework, and I'v