code: def setUp(self) -> None:
      self.root = tempfile.TemporaryDirectory()
      img = np.random.randint(0, 255, (30, 20, 3), dtype=np.uint8)
      cv2.imwrite(osp.join(self.root.name, "test_img.jpg"), img)
      self.instance = [
          {"poly": [0, 0, 0, 10, 10, 20, 20, 0], "ignore": False},
          {"box": [0, 0, 10, 20], "ignore": False},
      ]
      self.img_path = osp.join(self.root.name, "test_img.jpg")
      self.sample = (self.img_path, self.instance)
  
file_path: mmocr/tests/test_datasets/test_preparers/test_packers/test_textdet_packer.py
imports: import os.path
  import tempfile
  import unittest
  import cv2
  import numpy
  from mmocr.datasets.preparers import TextDetPacker
label_desc: Use image node_id 1 for calling the TestTextDetPacker obj's underlying member method code with example usage: obj.setUp() without return types