TreeCheckbox CSS visible folders

I am using the sephiroth checkbox tree and I'm trying to hide the folders and icons here is what I have as in inline开发者_如何学Python code, but it seems to not be working. Any suggestions why?

TreeCheckBox {
  backgroundAlpha: 0.0;
  folderClosedIcon: ClassReference(null);
  folderOpenIcon: ClassReference(null); 
  defaultLeafIcon: ClassReference(null);
}

That works for me, code follows:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" xmlns:controls="it.sephiroth.controls.*">
    <mx:XML id="wut">
        <node label="Mail Box">
            <node label="Inbox">
                <node label="Marketing"/>
                <node label="Product Management"/>
                <node label="Personal"/>
            </node>
            <node label="Outbox">
                <node label="Professional"/>
                <node label="Personal"/>
            </node>
            <node label="Spam"/>
            <node label="Sent"/>
        </node>
    </mx:XML>
    <mx:Style>
        TreeCheckBox {
      backgroundAlpha: 0.0;
      folderClosedIcon: ClassReference(null);
      folderOpenIcon: ClassReference(null); 
      defaultLeafIcon: ClassReference(null);
    }

    </mx:Style>
    <controls:TreeCheckBox dataProvider="{wut}" width="100%" height="100%" showRoot="true" labelField="@label" />
</mx:Application>

My guess would be that you're not linking the style file correctly in your application. As in:

<mx:Style source="/correct-path-relative-to-src/my.css" />