javascript - combineReducers这个方法的作用是什么

function visibilityFilter(){}
function todos(){}

import { combineReducers, createStore } from 'redux';
let reducer = combineReducers({ visibilityFilter, todos });
let store = createStore(reducer);

combineReducers这个方法把传进去的那个包含两个属性的对象怎么着了?