docs: def get_parser():
      """Argument specifier.
  
      """
  
      parser = argparse.ArgumentParser(prog='pyradigm')
  
      parser.add_argument('path_list', nargs='*', action='store',
                          default=None, help='List of paths to display info about.')
  
      parser.add_argument('-m', '--meta', action='store_true', dest='meta_requested',
                          required=False,
                          default=False, help='Prints the meta data (subject_id,class).')
  
      parser.add_argument('-i', '--info', action='store_true', dest='summary_requested',
                          required=False,
                          default=False,
                          help='Prints summary info (classes, #samples, #features).')
  
      arithmetic_group = parser.add_argument_group('Options for multiple datasets')
      arithmetic_group.add_argument('-a', '--add', nargs='+', action='store',
                                    dest='add_path_list', required=False,
                                    default=None,
                                    help='List of MLDatasets to combine')
  
      arithmetic_group.add_argument('-o', '--out_path', action='store', dest='out_path',
                                    required=False,
                                    default=None,
                                    help='Output path to save the resulting dataset.')
  
      return parser