code: def test_input_output_disconnect():
      input_node1 = ak.Input()
      output_node = input_node1
      _ = ak.DenseBlock()(output_node)
  
      input_node = ak.Input()
      output_node = input_node
      output_node = ak.DenseBlock()(output_node)
      output_node = ak.RegressionHead()(output_node)
  
      with pytest.raises(ValueError) as info:
          graph_module.Graph(inputs=input_node1, outputs=output_node)
      assert "Inputs and outputs not connected." 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 1 for calling a global function with example usage: test_input_output_disconnect() without return types