code: def write_list(path_out, image_list):
      
      with open(path_out, 'w') as fout:
          for i, item in enumerate(image_list):
              line = '%d\t' % item[0]
              for j in item[2:]:
                  line += '%f\t' % j
              line += '%s\n' % item[1]
              fout.write(line)
docs: Hepler function to write image list into the file.
      The format is as below,
      integer_image_index \t float_label_index \t path_to_image
      Note that the blank between number and tab is only used for readability.
      Parameters
      ----------
      path_out: string
      image_list: list