code: def test_postproc_nodes():
      """
      Test to check if the postproc_nodes method correctly process GraphNodes
      In the process of connecting nodes, GraphNode may appear in the pipeline,
      so the method should change their type to an acceptable one
  
      postproc_nodes method is called at the end of the update_node method
      """
  
      pipeline = get_pipeline()
  
      lda_node = pipeline.nodes[-2]
      qda_node = pipeline.nodes[-1]
  
      pipeline.connect_nodes(lda_node, qda_node)
  
      for node in pipeline.nodes:
          assert isinstance(node, PipelineNode)
  
imports: from fedot.core.pipelines.node import PipelineNode
  from fedot.core.pipelines.pipeline import Pipeline
  from golem.core.optimisers.graph import OptNode
label_desc: Use image node_id 2 for calling a global function with example usage: test_postproc_nodes() without return types