code: def test_input_missing():
      input_node1 = ak.Input()
      input_node2 = ak.Input()
      output_node1 = ak.DenseBlock()(input_node1)
      output_node2 = ak.DenseBlock()(input_node2)
      output_node = ak.Merge()([output_node1, output_node2])
      output_node = ak.RegressionHead()(output_node)
  
      with pytest.raises(ValueError) as info:
          graph_module.Graph(inputs=input_node1, outputs=output_node)
      assert "A required input is missing for HyperModel" in str(
          info.value
      )
  
file_path: autokeras/autokeras/graph_test.py
imports: import os
  import keras_tuner
  import pytest
  import autokeras
  from autokeras import graph
label_desc: Use image node_id 3 for calling a global function with example usage: test_input_missing() without return types