AttributeError: module 'matplotlib' has no attribute 'pyplot'

从 matplotlib_inline/backend_inline.py 第 100 行开始，这里 matplotlib.pyplot.close('all') 会引发报告中的 AttributeError。使用所示的 notebook 用法重现该失败，并将其与显式导入 matplotlib.pyplot 进行比较；当按描述使用 backend 时 inline 清理不再失败，即表示完成。

While attempting to create a piano roll with librosa and matplotlib, like this:

def plot_piano_roll(pm, start_pitch, end_pitch, fs=100):
    # Use librosa's specshow function for displaying the piano roll
    librosa.display.specshow(pm.get_piano_roll(fs)[start_pitch:end_pitch],
                             hop_length=1, sr=fs, x_axis='time', y_axis='cqt_note',
                             fmin=pretty_midi.note_number_to_hz(start_pitch))

plt.figure(figsize=(8, 4))
plot_piano_roll(pm, 56, 70)

I encounter this error:

AttributeError                            Traceback (most recent call last)
File ~/anaconda3/lib/python3.9/site-packages/matplotlib_inline/backend_inline.py:100, in show(close, block)
     97 # only call close('all') if any to close
     98 # close triggers gc.collect, which can be slow
     99 if close and Gcf.get_all_fig_managers():
--> 100     matplotlib.pyplot.close('all')

File ~/anaconda3/lib/python3.9/site-packages/matplotlib/_api/__init__.py:226, in caching_module_getattr.<locals>.__getattr__(name)
    224 if name in props:
    225     return props[name].__get__(instance)
--> 226 raise AttributeError(
    227     f"module {cls.__module__!r} has no attribute {name!r}")

AttributeError: module 'matplotlib' has no attribute 'pyplot'

The error seems to be fixed if I explicitly declare import matplotlib.pyplot as plt at the start of the file and then use that to call it like this: plt.close('all'). If that alone is satisfactory, I would request to do a PR.