element的导航菜单的展开收起图标怎么修改。

Question

 <div class="dci_dhList" :style="{'height':windowH+'px'}">
            <el-scrollbar style="height:100%">
                <el-menu default-active="activeMenu" style="border-right:'none'" @open="handleOpen" @close="handleClose">
                    <el-submenu :index="item.id" v-for="item in cityList" :key='item.id' :class="[item.checked ? 'border_active' :'border_normal']">
                        <template slot="title">
                            <span :class="[item.checked ? 'titleActive' :'']">{{item.title}}</span>
                            <!-- <i class="el-icon-location"></i> -->
                        </template>
                        <el-menu-item :index="itemC.key" v-for="itemC in item.children" :key="itemC.key" @click="clickItem(itemC.key)">
                            {{itemC.text}}
                        </el-menu-item>
                    </el-submenu>
                </el-menu>
            </el-scrollbar>
        </div>