code: def plot_all_spectra(self, outdir):
          
          os.makedirs(outdir, exist_ok=True)
  
          g = self.data.groupby('id')
          for nr, (name, item) in enumerate(g):
              print(
                  'Plotting spectrum with id {} ({} / {})'.format(
                      name, nr, len(g.groups.keys()))
              )
              plot_filename = ''.join((
                  outdir + os.sep,
                  '{:04}_spectrum_id_{}.png'.format(nr, name)
              ))
              spec_nor, spec_rec, spec_fig = self.get_spectrum(
                  nr_id=name,
                  plot_filename=plot_filename
              )
              plt.close(spec_fig)
docs: This is a convenience function to plot ALL spectra currently
          stored in the container. It is useful to asses whether data filters
          do perform correctly.
  
          Note that the function just iterates over all ids and plots the
          corresponding spectra, thus it is slow.
  
          Spectra a named using the format: \%.2i_spectrum_id_\{\}.png.
  
          Parameters
          ----------
          outdir : string
              Output directory to store spectra in. Created if it does not
              exist.