code: def test_load_png(self):
      spatial_size = (6, 6, 3)
      test_image = np.random.randint(0, 256, size=spatial_size)
      with tempfile.TemporaryDirectory() as tempdir:
          filename = os.path.join(tempdir, "test_image.png")
          Image.fromarray(test_image.astype("uint8")).save(filename)
          result = LoadImaged(keys="img")({"img": filename})
          result = EnsureChannelFirstd(keys="img")(result)
          self.assertEqual(result["img"].shape[0], 3)
  
file_path: MONAI/tests/test_ensure_channel_firstd.py
imports: from __future__ import annotations
  import os
  import tempfile
  import unittest
  import nibabel
  import numpy
  import torch
  from parameterized import parameterized
  from PIL import Image
  from monai.data.meta_tensor import MetaTensor
  from monai.transforms import EnsureChannelFirstd, LoadImaged
label_desc: Use image node_id 2 for calling the TestEnsureChannelFirstd obj's underlying member method code with example usage: obj.test_load_png() without return types