jstree hide child checkboxes and only show parent checkboxes

Is it possible to do this in CSS - I have tried a couple of things below which do not quite work. Basically I need to display checkboxes at the Parent level and hide all children, I have tried the following:

    .jstree-children > .jstree li.jstree-open >a.jstree-anchor >  i.jstree-checkbox { display:none;  }

    .jstree li.jstree-open   > a.jstree-anchor >  i.jstree-checkbox { display:none;  }

Any ideas??