I have few classes. `Test~` classes extend `FrameModel`. 

How can I create a map from `string` to subclasses of `FrameModel`?

```
import FrameModel from '../../FrameModel';
import TestShipModel from './TestGeneratorModel';
import TestGeneratorModel from './TestGeneratorModel';
import TestPlanetModel from './TestGeneratorModel';

export class DiscriminatorMappingData
{
    static mapping: { [key: string]: typeof FrameModel } = {
        "TestShip": TestShipModel,
        "TestGenerator": TestGeneratorModel,
        "TestPlanet": TestPlanetModel,
    }
}

```

This ends up with an error:

DiscriminatorMappingData.ts(8,5): error TS2322: Type '{ [x: string]: typeof "...' is not assignable to type '{ [key: string]: typeof "...'.  

 Index signatures are incompatible.  

 Type 'typeof "...models/T...' is not assignable to type 'typeof ".../FrameModel"'.  

 Property 'FrameModel' is missing in type 'typeof ".../models/T...'.

I assume this can be done with generics but I'm not sure how.