code: def checkArgs(args):
      
      # Check in input file
      if not os.path.isfile(args.file):
          msg = "%s: no such file" % args.file
          raise ProgramError(msg)
  
      # Check the population file
      if args.population_file is None:
          msg = "population-file: no population file"
          raise ProgramError(msg)
      elif not os.path.isfile(args.population_file):
          msg = "%s: no such file" % args.population_file
          raise ProgramError(msg)
  
      return True
docs: Checks the arguments and options.
  
      :param args: an object containing the options of the program.
  
      :type args: argparse.Namespace
  
      :returns: ``True`` if everything was OK.
  
      If there is a problem with an option, an exception is raised using the
      :py:class:`ProgramError` class, a message is printed to the
      :class:`sys.stderr` and the program exists with code 1.