docs: def checkArgs(args):
      """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.
  
      """
      # Checking if there are input files
      if args.summarized_intensities is None:
          if args.bfile is None and args.intensities is None:
              msg = ("need to specify either '--bfile' and '--intensities', or "
                     "'--summarized-intensities'")
              raise ProgramError(msg)
  
          # Checking the fam file bim
          for suffix in {".bim", ".fam"}:
              if not os.path.isfile(args.bfile + suffix):
                  msg = "{}: no such file".format(args.bfile + suffix)
                  raise ProgramError(msg)
  
          # Checking the intensity file
          if not os.path.isfile(args.intensities):
              msg = "{}: no such file".format(args.intensities)
              raise ProgramError(msg)
      else:
          if args.bfile is not None or args.intensities is not None:
              msg = ("need to specify either '--bfile' and '--intensities', or "
                     "'--summarized-intensities'")
              raise ProgramError(msg)
  
          for suffix in {".ok_females.txt", ".ok_males.txt", ".ok_unknowns.txt",
                         ".problematic_females.txt", ".problematic_males.txt",
                         ".problematic_unknowns.txt"}:
              if not os.path.isfile(args.summarized_intensities + suffix):
                  msg = "{}: no such file".format(args.summarized_intensities +
                                                  suffix)
                  raise ProgramError(msg)
  
      # Checking the sex problem file
      if args.sex_problems is not None:
          if not os.path.isfile(args.sex_problems):
              msg = "{}: no such file".format(args.sex_problems)
              raise ProgramError(msg)
  
      return True