code: def input_spec(self):
      return {
          "image": lit_types.ImageBytes(),
          "grad_target": lit_types.CategoryLabel(
              vocab=self.LABELS, required=False
          ),
      }
  
imports: from absl.testing import absltest
  from lit_nlp.api import dataset
  from lit_nlp.api import model
  from lit_nlp.api import types
  from lit_nlp.components import image_gradient_maps
  from lit_nlp.lib import image_utils
  import numpy
  from PIL import Image
label_desc: Use image node_id 3 for calling the ClassificationTestModel obj's underlying member method code with example usage: obj.input_spec() and returns: dict