не работают графики, говорит про ошибку matplotlib

An error occurred. It may have been caused by a harmless bug, 
or your deck may have a problem. 
To confirm it's not a problem with your deck, please restart
Anki and run Tools > Advanced > Check Database. 
If that doesn't fix the problem, please copy the following
into a bug report:

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ankiqt/ui/main.py", line 1876, in onShowGraph
    ui.dialogs.get("Graphs", self, self.deck)
  File "/usr/lib/python2.7/site-packages/ankiqt/ui/__init__.py", line 53, in get
    return klass(*args)
  File "/usr/lib/python2.7/site-packages/ankiqt/ui/__init__.py", line 64, in graphProxy
    import graphs
  File "/usr/lib/python2.7/site-packages/ankiqt/ui/graphs.py", line 12, in 
    from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
ImportError: No module named backend_qt4agg

Кроме того было бы хорошо обновить версию.