docs: def _backup(path, filename):
      """
      Backup a file.
      """
      target = os.path.join(path, filename)
      if os.path.isfile(target):
          dt = datetime.now()
          new_filename = ".{0}.{1}.{2}".format(
              filename, dt.isoformat(), "backup"
          )
          destination = os.path.join(path, new_filename)
          puts("- Backing up {0} to {1}".format(
              colored.cyan(target),
              colored.cyan(destination)
          ))
  
          shutil.copy(target, destination)