code: def ensure_list(path_or_path_list):
      
      if isinstance(path_or_path_list, (tuple, list, set)):
          return [ensure_str(path) for path in path_or_path_list]
      else:
          return [ensure_str(path_or_path_list), ]
docs: Pre-process input argument, whether if it is:
  
      1. abspath
      2. Path instance
      3. string
      4. list or set of any of them
  
      It returns list of path.
  
      :return path_or_path_list: always return list of path in string
  
      **中文文档**
  
      预处理输入参数。