code: def main(argv=None):
      
      # Exit code
      exit_code = 0
  
      # First, we change main() to take an optional 'argv'
      # argument, which allows us to call it from the interactive
      # Python prompt
      if argv is None:
          argv = sys.argv
  
      try:
          # Bootstrap
          init(argv)
  
          # Perform the actual backup job
          make_backup_files()
  
      except Exception as e:
          # ... and if everything else fails
          _handle_except(e)
          exit_code = 1
      finally:
          # All cleanup actions are taken from here
          shutdown()
          return exit_code
docs: This is the main thread of execution
  
      :param argv: list of command line arguments