@Override
 public Collection<AbstractTreeNode> getChildrenImpl() {
   PyFile value = (PyFile) getValue();
   List<AbstractTreeNode> children = new ArrayList<AbstractTreeNode>();
   for (PyClass child : value.getTopLevelClasses()) {
     children.add(new PyElementNode(myProject, child, getSettings()));
   }
   for (PyFunction function : value.getTopLevelFunctions()) {
     children.add(new PyElementNode(myProject, function, getSettings()));
   }
   return children;
 }