Ошибка при разработке блока square_ff на grc

Question

Я пытаюсь разработать пример модуля OOT square_ff. Я следил за каждым шагом, но при попытке перетаскивания по экрану на grc выдает ошибку.

    Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/ActionHandler.py", line 337, in _handle_action
    self.get_flow_graph().update()
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/FlowGraph.py", line 348, in update
    self.create_labels()
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/Element.py", line 78, in create_labels
    for child in self.get_children():child.create_labels()
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/Block.py", line 157, in create_labels
    markups = [param.get_markup() for param in self.get_params() if param.get_hide() not in ('all', 'part')]
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/python/Param.py", line 173, in get_hide
    lambda p: ' '.join([p._type, p._nports]), self.get_parent().get_ports())
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/python/Param.py", line 173, in <lambda>
    lambda p: ' '.join([p._type, p._nports]), self.get_parent().get_ports())
TypeError: sequence item 0: expected string, instance found
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/DrawingArea.py", line 142, in _handle_window_expose
    self._flow_graph.draw(gc, self._pixmap)
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/FlowGraph.py", line 317, in draw
    element.draw(gc, window)
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/grc/gui/Block.py", line 227, in draw
    window.draw_drawable(gc, self.horizontal_label, 0, 0, x+BLOCK_LABEL_PADDING, y+(self.H-self.label_height)/2, -1, -1)
AttributeError: 'Block' object has no attribute 'horizontal_label'