code: def classification_three_depth_manual_pipeline():
      """
      Returns pipeline with the following structure:
  
      .. image:: img_classification_pipelines/manual_three_depth_pipeline.png
        :width: 55%
  
      Where rf - xg boost classifier, logit - logistic regression, knn - K nearest neighbors classifier,
      qda - discriminant analysis
      """
      logit_node_primary = PipelineNode("logit")
      xgb_node_primary = PipelineNode("rf")
      xgb_node_primary_second = PipelineNode("rf")
  
      qda_node_third = PipelineNode(
          "qda", nodes_from=[xgb_node_primary_second]
      )
      knn_node_third = PipelineNode(
          "knn", nodes_from=[logit_node_primary, xgb_node_primary]
      )
  
      knn_root = PipelineNode(
          "knn", nodes_from=[qda_node_third, knn_node_third]
      )
  
      pipeline = Pipeline(knn_root)
  
      return pipeline
  
file_path: FEDOT/examples/simple/classification/classification_pipelines.py
imports: from fedot.core.pipelines.node import PipelineNode
  from fedot.core.pipelines.pipeline import Pipeline
label_desc: Use image node_id 8 for calling a global function with example usage: classification_three_depth_manual_pipeline() and returns: pipeline