code: function createModuleReducer(reducers) {
    var _reducersType = t.nullable(t.ref(ReducerDictionaryType$1));
  
    t.param('reducers', _reducersType).assert(reducers);
    return reducers ? redux.combineReducers(reducers) : function () {
      var state = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : null;
      return state;
    };
  }
docs: https://github.com/insin/react-examples/tree/master/code-splitting-redux-reducers https://medium.com/@luigiplr/react-redux-react-router-4-code-splitting-w-rxjs-webpack-32eabedf0e9 https://gist.github.com/gaearon/0a2213881b5d53973514 https://github.com/zeit/next.js/pull/1459