old_contents: import ROOT
  ROOT.PyConfig.IgnoreCommandLineOptions = True
  from Logger import Logger
  
  
  class InvalidInputError(ValueError):
      pass
  
  _logger = Logger().retrieve_logger()
  
  """
  Setting memory policy to avoid graphics objects getting deleted once drawn to canvas and canvas passing around.
  """
  ROOT.SetMemoryPolicy(ROOT.kMemoryStrict)
  
new_contents: import ROOT
  ROOT.PyConfig.IgnoreCommandLineOptions = True
  from Logger import Logger
  import argparse
  
  
  class InvalidInputError(ValueError):
      pass
  
  _logger = Logger().retrieve_logger()
  
  """
  Setting memory policy to avoid graphics objects getting deleted once drawn to canvas and canvas passing around.
  """
  ROOT.SetMemoryPolicy(ROOT.kMemoryStrict)
  
  
  def get_default_argparser(description=''):
      """
      Build default argument parser and add common args
      :param description: description printed when called with --help
      :type description: str
      :return: parser
      :rtype: argparse.ArgumentParser
      """
  
      parser = argparse.ArgumentParser(description=description)
      parser.add_argument('--log_level', '-log', default='info', help='log level')
      return parser
  
  
  def default_init(parser):
      """
      default initialisation of steering scripts and parsing of arguments
      :param parser: argument parser
      :type parser: argparse.ArgumentParser
      :return: parsed arguments
      :rtype: Namespace
      """
  
      args = parser.parse_args()
      Logger.set_log_level(_logger, args.log_level)
      return args
  
subject: implement default argparser