def METHOD_NAME(self):
    if self._x is not None:
        x = self._x
        nan_mean = np.nanmean(x)
        idx = np.isnan(x)
        x[idx] = nan_mean
        data = stft(x, self._n_fft, self._step, self._fs, self._window)
        data = np.abs(data)
        data = 20 * np.log10(data) if self._color_scale == 'log' else data
        if self._normalize:
            for i in range(data.shape[0]):
                data[i, :] -= np.mean(data[i, :])
                data[i, :] /= np.std(data[i, :])
        return data.astype(np.float32)  # ImageVisual will warn if 64-bit
    else:
        return None