code: def test(self, use_cpu_only, backend, rank, axis):
      shape = np.random.randint(low=2, high=4, size=rank)
      inputs = []
      for _ in range(2):
          inputs.append(
              tf.keras.layers.Input(batch_input_shape=tuple(shape))
          )
      out = tf.keras.layers.Concatenate(axis=axis)(inputs)
      model = tf.keras.Model(inputs=inputs, outputs=out)
      run_compare_tf_keras(
          model,
          [random_gen(shape), random_gen(shape)],
          use_cpu_only=use_cpu_only,
          backend=backend,
      )
  
imports: import random
  from coremltools.converters.mil import testing_reqs
  from coremltools.converters.mil.frontend.tensorflow2.test.testing_utils import run_compare_tf_keras
  from coremltools.converters.mil.testing_reqs import *
label_desc: Use image node_id 1 for calling the TestConcatenate obj's underlying member method code with example usage: obj.test(use_cpu_only, backend, rank, axis) without return types