code: def pipeline_fourth():
      #      RF
      #   |  \  \
      #  KNN  RF  KNN
      #      |  \
      #    KNN   KNN
  
      pipeline = pipeline_third()
      new_node = PipelineNode("rf")
      [
          new_node.nodes_from.append(PipelineNode("knn"))
          for _ in range(2)
      ]
      pipeline.update_subtree(
          pipeline.root_node.nodes_from[1], new_node
      )
  
      return pipeline
  
file_path: FEDOT/test/unit/pipelines/test_pipeline_comparison.py
imports: import itertools
  from copy import deepcopy
  import pytest
  from fedot.core.pipelines.node import PipelineNode
  from fedot.core.pipelines.pipeline import Pipeline
label_desc: Use image node_id 4 for calling a global function with example usage: pipeline_fourth() and returns: pipeline