docs: def list_files(scan_path, contains=None):
      """
      Returns a list of all files in a folder, without subfolders (only files).
      """
      file_list = []
      path = os.path.abspath(scan_path)
      for f in sorted(os.listdir(path)):
          if contains and f.find(contains) < 0:
              continue
          filepath = os.path.join(path, f)
          if os.path.isfile(filepath):
              file_list.append(filepath)
      return file_list