code: def test_keras_not_available_exception(datadir):
      with pytest.raises(DeferredImportError):
          NN = keras.models.load_model(
              datadir.file("keras_linear_131_relu")
          )
  
imports: import numpy
  import pyomo.environ
  import pytest
  from pyomo.common.dependencies import DeferredImportError
  from omlt.dependencies import keras, keras_available
  from conftest import get_neural_network_data
  from omlt.block import OmltBlock
  from omlt.neuralnet import FullSpaceNNFormulation, ReducedSpaceNNFormulation
  from omlt.neuralnet.activations import ComplementarityReLUActivation
  from omlt.scaling import OffsetScaling
label_desc: Use image node_id 1 for calling a global function with example usage: test_keras_not_available_exception(datadir) without return types