title: jsTree show expand/collapse icon dynamically
body: <p>I am using jsTree with "data" option where in I fetch the JSON data myself (instead of using jsTree's AJAX option) and then render the tree.</p>
  
  <p>How do I show the expand/collapse icon programmatically? i.e. if I know the number of child nodes for a particular node, can I show the expand icon and then have an event attached to it so that I can lazy load the child nodes?</p>
  
  <p>I tried setting li_attr["class"]="jstree-closed" but it ends up adding this class to the already present "jstree-leaf" class on the 'li' node and so the expand icon does not show up.</p>