docs: def create_spectrum(spectrum_name):
          """Initialize spectrum and peak descriptions.
  
          :param str spectrum_name: Name of the spectrum from which peak list will be simulated.
          :return: Spectrum object.
          :rtype: :class:`~nmrstarlib.plsimulator.Spectrum`
          """
          try:
              spectrum_description = nmrstarlib.SPECTRUM_DESCRIPTIONS[spectrum_name]
          except KeyError:
              raise NotImplementedError("Experiment type is not defined.")
  
          spectrum = plsimulator.Spectrum(spectrum_name, spectrum_description["Labels"],
                                          spectrum_description["MinNumberPeaksPerSpinSystem"],
                                          spectrum_description.get("ResonanceLimit", None))
  
          for peak_descr in spectrum_description["PeakDescriptions"]:
              spectrum.append(plsimulator.PeakDescription(peak_descr["fraction"], peak_descr["dimensions"]))
  
          return spectrum