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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def list_spectrum_descriptions(*args):
 """List all available spectrum descriptions that can be used for peak list simulation. :param str args: Spectrum name(s), e.g. list_spectrum_descriptions("HNCO", "HNcoCACB"), leave empty to list everything. :return: None :rtype: :py:obj:`None` """

    if args:
        for spectrum_name in args:
            pprint.pprint({spectrum_name: SPECTRUM_DESCRIPTIONS.get(spectrum_name, None)}, width=120)
    else:
        pprint.pprint(SPECTRUM_DESCRIPTIONS, width=120)