def next_child(self, key):

        index = self.get_child_index(key)
        # the given node may have just been deleted
        if index is None:
            return None
        index += 1
        
        child_keys = self.get_child_keys()
        if index < len(child_keys):
            # get the next item at same level
            return self.get_child_node(child_keys[index])
        else:
            return None
Return the next child node in index order from the given key.
dataset/ETHPy150Open AnyMesh/anyMesh-Python/example/urwid/treetools.py/ParentNode.next_child