I am building a custom wrapper/driver around the package MNE-Python that does realtime EEG signal analysis. I am taking a static-class approach and has methods like these:

    @staticmethod
    def plot_psd(mne_driver, *args, **kwargs):
        psd_fig = mne_driver.mne_raw.compute_psd().plot(*args, **kwargs)
        if mne_driver.output_destination is not None:
            psd_fig.savefig(mne_driver.get_path_name("psd.png"))
        mne_driver.sequence += 1
        return mne_driver

    @staticmethod
    def plot_topomap(mne_driver, *args, **kwargs):
        topomap_fig = mne_driver.mne_raw.compute_psd().plot_topomap(*args, **kwargs)   
        if mne_driver.output_destination is not None:
            topomap_fig.savefig(mne_driver.get_path_name("topomap.png"))
        mne_driver.sequence += 1
        return mne_driver

where mne_driver.mne_raw is an mne.io.Raw object.

When I plot the PSD graph, it gets saved correctly to the predefined location. However, when I plot the PSD topomap, it does not get saved; instead, the program seems to stop proceeding after executing the line topomap_fig = mne_driver.mne_raw.compute_psd().plot_topomap(*args, **kwargs): it opens the window containing the correct, functioning graph and does not go on to the next line of code.

According to MNE-Python’s documentation, both Raw.compute_psd().plot() and compute_psd().plot_topomap() shall return a Matplotlib Figure object, which could then be saved.

Thus, I am curious whether there is a difference in the implementation of the two methods the causing the saving behavior to be different, and if so, how could I fix this?