Work with reducers from packages such as apollo stack/redux-form

Apollo stack has to check apollo reducer in combined reducer, in redux-loop way, reducer is been transformed into immutable way.
The same problem happened when using redux-form

```
import {createStore, combineReducers} from 'redux';
import {reducer as formReducer} from 'redux-form';
const reducers = {
// ... your other reducers here ...
form: formReducer // <---- Mounted at 'form'. See note below.
}
const reducer = combineReducers(reducers);
const store = createStore(reducer);

```

Is there any way to separate the imported reducer to use no immutable way?

Start by examining the combined reducer and the redux-loop transformation described in the issue, then reproduce the behavior with the Apollo and redux-form reducer examples. Done means determining whether imported reducers can remain non-immutable while being combined, and documenting or implementing a supported separation if needed.

Written by the indexing model from the issue text.