求大神，python 操作frame下的js，找不到元素

网页源码： <script language="JavaScript" type="text/JavaScript"> function showSubMenu(parentName,menuName,obj){ //导航栏信息显示 parent.parent.frames["banner"].document.getElementById("top_menuLevel1").innerHTML = parentName+"  "; parent.parent.frames["banner"].document.getElementById("top_menuLevel2").innerHTML = menuName; parent.parent.frames["banner"].document.getElementById("top_menuLevel2").className="next"; parent.parent.frames["banner"].document.getElementById("top_menuLevel1").className="next"; var obj1=parent.parent.frames["serv"]; if(obj1!='undefined'&&obj1!=null){ var myParm= obj1.document.getElementById("common.parm").value;
myParm=myParm.split(','); var urlParm=""; for(var i=0;i<myParm.length;i++){ if(myParm[i]!=''){ if(urlParm.indexOf(myParm[i]) < 0){ if(i==0){ urlParm="&"+myParm[i]; }else{ urlParm=urlParm+"&"+myParm[i]; } } } }

    if(urlParm!=''){
        //tanghua by 2012-3-19 CMS来回点击菜单后，页面不出来的BUG修改，原因是URL后面拼接的参数重复所致
        if(obj.href.indexOf(urlParm) < 0){
            obj.href = obj.href + urlParm;
        }
    }
}

} </script></head>

        <dl>
            <dt><span><i class="ico1"></i><em>平台管理</em></span></dt>
            <dd>
                <ul>

                    <li>


                        <a title="管理主页" href="http://manage.zjer.cn/aam/manage/jumpTo.action?service=http://portalDomain//index.php?r=center/portal/baseinfo%26fromtype=aama&amp;platformCode=331002" target="main" onclick="showSubMenu('平台管理','管理主页',this)">管理主页</a>

                        <div class="ni_g_3menu">
                            <div class="ni_hight">

                            </div>

                        </div>
                    </li>

wbe.get('http://jiaojiang.m.zjer.cn/aam/acl/index.jsp?platformCode=331002&sub=portal5&openType=2') wbe.switch_to.frame('leftmenu') aa=wbe.find_elements_by_link_text('资讯管理') 找不到该元素，打不开main，

<a title="平台信息管理" href="http://manage.zjer.cn/aam/manage/jumpTo.action?service=http://portalDomain//index.php?r=center/portal/baseinfo/manage%26fromtype=aamadmin&platformCode=331002" target="main" onclick="showSubMenu('平台管理','平台信息管理',this)">平台信息管理</a>

如何执行js?