使用Django查询获取相关模型

Can you please help me with Django query. I am new in this stuff and I am trying to optimize the queries in my site. Below is the current case: I use the standard User model as base model and have 3 types of users, which are related with it: A, B and C. "User" can be related with only one of these 3 model. Currently I have a list with instance from Model D, which is related with User as well. Below is my codeCan you please help me with Django query. I am