code: def get_modelnames() -> List[str]:
          
          return sorted(str(fn.split('.')[0])
                        for fn in os.listdir(models.__path__[0])
                        if (fn.endswith('.py') and (fn != '__init__.py')))
docs: Return a sorted |list| containing all application model names.
  
          >>> from hydpy.auxs.xmltools import XSDWriter
          >>> print(XSDWriter.get_modelnames())    # doctest: +ELLIPSIS
          [...'dam_v001', 'dam_v002', 'dam_v003', 'dam_v004', 'dam_v005',...]