code: def test_image_nested_empty_len(self):
      imgs = [
          np.random.randint(256, size=(28, 28, 3), dtype=np.uint8),
          np.random.randint(256, size=(28, 28, 3), dtype=np.uint8),
      ]
      imgs_stacked = np.stack(imgs)
  
      self.assertFeature(
          feature=feature_lib.Sequence(
              {
                  "a": feature_lib.Image(shape=(None, None, 3)),
                  "b": np.int32,
              }
          ),
          shape={
              "a": (None, None, None, 3),
              "b": (None,),
          },
          dtype={
              "a": np.uint8,
              "b": np.int32,
          },
          tests=[
              testing.FeatureExpectationItem(
                  value={
                      "a": imgs,
                      "b": [1, 2],
                  },
                  expected={
                      "a": imgs_stacked,
                      "b": [1, 2],
                  },
                  expected_np={
                      "a": imgs_stacked,
                      "b": [1, 2],
                  },
              ),
              testing.FeatureExpectationItem(
                  value={
                      "a": [],
                      "b": [],
                  },
                  expected={
                      "a": np.empty(shape=(0, 0, 0, 3), dtype=np.uint8),
                      "b": [],
                  },
                  expected_np={
                      "a": np.empty(shape=(0, 0, 0, 3), dtype=np.uint8),
                      "b": [],
                  },
              ),
          ],
      )
  
imports: import numpy
  import tensorflow
  from tensorflow_datasets import testing
  from tensorflow_datasets.core import features
label_desc: Use image node_id 4 for calling the SequenceFeatureTest obj's underlying member method code with example usage: obj.test_image_nested_empty_len() without return types