code: def _build_model():
      """Builds a simple CNN model."""
      i = tf.keras.layers.Input(shape=(28, 28), name="input")
      x = tf.keras.layers.Reshape((28, 28, 1))(i)
      x = tf.keras.layers.Conv2D(
          filters=NUMBER_OF_CHANNELS,
          kernel_size=(3, 3),
          activation="relu",
          name="conv1",
      )(x)
      x = tf.keras.layers.MaxPool2D(2, 2)(x)
      x = tf.keras.layers.Flatten()(x)
      output = tf.keras.layers.Dense(units=10)(x)
  
      model = tf.keras.Model(inputs=[i], outputs=[output])
      return model
  
file_path: model-optimization/tensorflow_model_optimization/python/core/clustering/keras/mnist_clustering_test.py
imports: from absl.testing import parameterized
  import tensorflow
  from tensorflow_model_optimization.python.core.clustering.keras import cluster
  from tensorflow_model_optimization.python.core.clustering.keras import cluster_config
label_desc: Use image node_id 1 for calling a global function with example usage: _build_model() and returns: model