如何让这个天气覆盖在Python中正常工作？

Question

我想用来自http://mesonet.agron.iastate.edu/cgi-bin/wms/nexrad/n0r.cgi的天气数据覆盖一张地图，但是看起来像是天气图去掉了背景地图，这样美国地图就可以看到了。对Python还不熟悉，想要在上面覆盖天气，但我没有做正确的事情-提前感谢您的建议。你知道吗

from ipyleaflet import (
    Map, basemaps, basemap_to_tiles,
    Marker, DrawControl, WMSLayer)
m = Map(center=(39, -98), zoom=4, basemap=basemaps.Esri.DeLorme) 
marker = Marker(location=(39, -98))
dc=DrawControl(circle={'shapeOptions':{'color':'#0000FF'}})
wms = WMSLayer(
    url="http://mesonet.agron.iastate.edu/cgi-bin/wms/nexrad/n0r.cgi",
    layers = "nexrad-n0r-900913",
            fmt='image/png',
            attr=u'Weather data © 2012 IEM Nexrad',
        transparent=True)
m.add_layer(marker)
m.add_control(dc)
m.add_layer(wms)
m