class_docstr: Unit tests for KerasLayer.
class_docstr_tok: ["Unit","tests","for","KerasLayer","."]
code: def test_keras_layer_fails_if_signature_trainable(self):
      export_dir = os.path.join(
          self.get_temp_dir(), "saved_model_v2_mini"
      )
      _save_plus_one_saved_model_v2(export_dir, save_from_keras=False)
      layer = hub.KerasLayer(
          export_dir,
          signature="serving_default",
          signature_outputs_as_dict=True,
          trainable=True,
      )
      layer.trainable = True
      with self.assertRaisesRegex(
          ValueError, "trainable.*=.*True.*unsupported"
      ):
          layer(10.0)
  
imports: import json
  import os
  from absl.testing import parameterized
  import numpy
  import tensorflow
  import tensorflow_hub
label_desc: Use image node_id 10 for calling the KerasLayerTest obj's underlying member method code with example usage: obj.test_keras_layer_fails_if_signature_trainable() without return types