[typescript-graphql-request] importOperationTypesFrom does nothing

**Describe the bug**
The docs for typescript-graphql-request describe that importOperationTypesFrom could be used to import the operations from another file. But whatever I do, it seems to do nothing.

**To Reproduce**
Codesandbox: https://codesandbox.io/s/boring-paper-rsces?file=/codegen.yml

**Additional context**
I made it work with this snipped. Bu I think importOperationTypesFrom should do that for me.

>
> plugins:
> - add:
> content: "import * as Types from './types';"
> - typescript-graphql-request
> config:
> typesPrefix: Types.
>