code: def _parse_sparkml_pipeline(spark, scope, model, global_inputs, output_dict):
      '''
      The basic ideas of spark-ml parsing:
          1. Sequentially go though all stages defined in the considered spark-ml pipeline
          2. The output variables of one stage will be fed into its next stage as the inputs.
  
      :param scope: Scope object defined in _topology.py
      :param model: spark-ml pipeline object
      :param global_inputs: A list of Variable objects
      :param output_dict: An accumulated list of output_original_name->(ref_count, variable)
      :return: A list of output variables produced by the input pipeline
      '''
      for stage in model.stages:
          _parse_sparkml(spark, scope, stage, global_inputs, output_dictf _parse_sparkml_pipeline(spark, scope, model, global_inputs, output_dict):
      '''
      The basic ideas of spark-ml parsing:
          1. Sequentially go though all stages defined in the considered spark-ml pipeline
          2. The output variables of one stage will be fed into its next stage as the inputs.
  
      :param scope: Scope object defined in _topology.py
      :param model: spark-ml pipeline object
      :param global_inputs: A list of Variable objects
      :param output_dict: An accumulated list of output_original_name->(ref_count, variable)
      :return: A list of output variables produced by the input pipeline
      '''
      for stage in model.stages:
          _parse_sparkml(spark, scope, stage, global_inputs, output_dict)
docs: The basic ideas of spark-ml parsing:
          1. Sequentially go though all stages defined in the considered spark-ml pipeline
          2. The output variables of one stage will be fed into its next stage as the inputs.
  
      :param scope: Scope object defined in _topology.py
      :param model: spark-ml pipeline object
      :param global_inputs: A list of Variable objects
      :param output_dict: An accumulated list of output_original_name->(ref_count, variable)
      :return: A list of output variables produced by the input pipeline