error: `JsonData(...)` returns a dynamic result, and thus must be assigned to a variable with a type annotation
--> main.sml:1:29
     |
   1 | Foo = Entity(type='User', id=JsonData(path='$.foo'))
     |                              ^ assign it to a variable before using it:
                                    | `SomeVariable: str = JsonData(path='$.foo')`
                                    | `Foo = Entity(type='User', id=SomeVariable)`