Circular references json in flutter

I have this code retrieved by my api developed in .net entityframework core.

User:{id:1,{Foo{id:1,prop:1}}, FooList{$ref: "1",Foo{id:2,prop:13}}

In Json.net I have the capacity to deserialize and serialize by using

PreserveReferencesHandling = PreserveReferencesHandling.Objects

Then my app is developed in flutter. I use jsonDecode( but I have an error because circular references are not managed.

How can I manage my flutter code to manage circular references?

Thanks,