django 中serializer 添加自定义字段

class BasicInfoHostRetrieveSerializer(serializers.ModelSerializer):
    ......
    cpu_used = serializers.SerializerMethodField()
    mem_used = serializers.SerializerMethodField()
    to_basic_info = BasicInfoSelectSerializer(many=True)   # 当to_basic_info是个多对多字段时，可以自己写一个BasicInfoSelectSerializer，，关联Basicinfo这个类，，定义显示的字段
    
    class Meta:
    model = BasicInfo
    fields = [......, 'cpu_used', 'mem_used', "to_basic_info" ]
    
    
    def get_cpu_used(self, obj):
       return xxx

serializer中获取get请求参数的方法

start_time = self.context["request"].query_params.get("start_time", None)