def iterate_open_nodes(self, node=None):
        if not node:
            node = self.root
        if self.hide_root and node is self.root:
            pass
        else:
            yield node
        if not node.is_open:
            return
        f = self.iterate_open_nodes
        for cnode in node.nodes:
            for ynode in f(cnode):
                yield ynode
Generator to iterate over all the expended nodes starting from
dataset/ETHPy150Open kivy/kivy/kivy/uix/treeview.py/TreeView.iterate_open_nodes