Typed immutable map for redux state

gistfile1.ts

type StateType = {
    router: RouterState;
    someReducer: Immutable.Map<keyof SomeReducerType, SomeReducerType[keyof SomeReducerType]>;
}

export interface AppStateInterface extends Immutable.Map<string, any> {
    toJS(): StateType;
    get<K extends keyof StateType>(key: K, notSetValue?: StateType[K]): StateType[K];
    set<K extends keyof StateType>(key: K, value: StateType[K]): this;
    has(key: string): key is keyof StateType;
    merge(...collections: Array<Partial<StateType> | Iterable<[string, any]>>): this;
    mergeDeep(...collections: Array<Partial<StateType> | Iterable<[string, any]>>): this;
}