code: def persist_as_png(structure_dict, filepath):
      
      graph = _create_graph(structure_dict)
      graph.write(filepath, format='png')
docs: Saves pipeline diagram to disk as png file.
  
      Args:
          structure_dict (dict): dict returned by
              :func:`~steppy.base.Step.upstream_structure`
          filepath (str): filepath to which the png with pipeline visualization should be persisted