godot get_next_node

get_next_node.gd

func get_next_node(node):
    var children = node.get_children()
    if children:
        return children[0]
    else:
        return _get_next_node_inner(node)

func _get_next_node_inner(node):
    var node_idx = node.get_index()
    var parent = node.get_parent()
    var siblings_count = parent.get_child_count()
    
    if siblings_count > node_idx+1:
        return parent.get_child(node_idx+1)
    else:
        if parent.filename:
            return null
        else:
            return _get_next_node_inner(parent)

it seems it's broken