code: def test_tuple_input_model_subclass(self):
      # https://github.com/keras-team/keras/issues/324
  
      class MultiInputModel(Model):
          def __init__(self, **kwargs):
              super().__init__(**kwargs)
              self.dense1 = layers.Dense(4)
  
          def call(self, inputs):
              a, b = inputs
              r = self.dense1(a)
              return layers.concatenate([r, b])
  
      model = MultiInputModel()
      x1 = np.random.rand(3, 3)
      x2 = np.random.rand(3, 2)
      out = model((x1, x2))
      self.assertEqual(out.shape, (3, 6))
  
imports: import numpy
  import pytest
  from absl.testing import parameterized
  from keras import layers
  from keras import testing
  from keras.layers.core.input_layer import Input
  from keras.models.functional import Functional
  from keras.models.model import Model
  from keras.models.model import model_from_json
label_desc: Use image node_id 3 for calling the ModelTest obj's underlying member method code with example usage: obj.test_tuple_input_model_subclass() and returns: layers