Traceback (most recent call last):

  File "<ipython-input-12-d73b5c362b1b>", line 1, in <module>
    f.savefig('test.eps')

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\figure.py", line 2180, in savefig
    self.canvas.print_figure(fname, **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_qt5agg.py", line 88, in print_figure
    super().print_figure(*args, **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backend_bases.py", line 2082, in print_figure
    **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 842, in print_eps
    return self._print_ps(outfile, 'eps', *args, **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 871, in _print_ps
    **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 966, in _print_figure
    self.figure.draw(renderer)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\figure.py", line 1709, in draw
    renderer, self, artists, self.suppressComposite)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\image.py", line 135, in _draw_list_compositing_images
    a.draw(renderer)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2647, in draw
    mimage._draw_list_compositing_images(renderer, self, artists)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\image.py", line 135, in _draw_list_compositing_images
    a.draw(renderer)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\collections.py", line 329, in draw
    self._offset_position)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 492, in draw_path_collection
    offset_position)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backend_bases.py", line 245, in draw_path_collection
    self.draw_path(gc0, path, transform, rgbFace)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 414, in draw_path
    self._draw_ps(ps, gc, rgbFace)

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 759, in _draw_ps
    self.set_linedash(*gc.get_dashes())

  File "C:\Users\mhossein\Anaconda3\lib\site-packages\matplotlib\backends\backend_ps.py", line 276, in set_linedash
    s = "[%s] %d setdash\n" % (_nums_to_str(*seq), offset)

TypeError: %d format: a number is required, not NoneType