code: def test_keras_saved_model_file(self, backend):
      keras_model = tf.keras.Sequential(
          [
              tf.keras.layers.Flatten(
                  input_shape=(28, 28), batch_size=1
              ),
              tf.keras.layers.Dense(10, activation=tf.nn.relu),
          ]
      )
      keras_model.save(self.saved_model_dir, save_format="tf")
      mlmodel = converter.convert(
          self.saved_model_dir,
          outputs=["Identity"],
          source=frontend,
          convert_to=backend[0],
      )
      assert mlmodel is not None
  
imports: import os
  import shutil
  import tempfile
  import pytest
  import coremltools.converters
  from coremltools.converters.mil.frontend.tensorflow.test.test_load import frontend
  from coremltools.converters.mil.frontend.tensorflow.test.testing_utils import get_tf_keras_io_names
  from coremltools.converters.mil.input_types import TensorType
  from coremltools.converters.mil.testing_reqs import backends
label_desc: Use image node_id 4 for calling the TestTf2ModelFormats obj's underlying member method code with example usage: obj.test_keras_saved_model_file(backend) without return types