code: def persist_intermediate(self, ddf, folder):
      path = os.path.join(self.args.output_path, folder)
      logging.info(f"Persisting intermediate results to {path}")
      ddf.to_parquet(path)
      del ddf
      gc.collect()
      ddf = self.df_lib.read_parquet(path)
      return ddf
  
imports: import gc
  import logging
  import os
  import shutil
  from functools import reduce
  from typing import Optional
  import nvtabular
  from merlin.core.dispatch import HAS_GPU
  from merlin.schema import Tags
  from nvtabular import ops
  from .args_parsing import parse_arguments
label_desc: Use image node_id 11 for calling the PreprocessingRunner obj's underlying member method code with example usage: obj.persist_intermediate(ddf, folder) and returns: ddf