docs: def default_filename_decoder():
      """
      Creates a decoder which parses CWR filenames following the old or the new
      convention.
  
      :return: a CWR filename decoder for the old and the new conventions
      """
      factory = default_filename_grammar_factory()
  
      grammar_old = factory.get_rule('filename_old')
      grammar_new = factory.get_rule('filename_new')
  
      return FileNameDecoder(grammar_old, grammar_new)