docs: def ingest_mp(b, stage, source_name, clean_files):
      """Ingest a source, using only arguments that can be pickled, for multiprocessing access"""
  
      source = b.source(source_name)
  
      with b.progress.start('ingest_mp',0,message="MP ingestion", source=source) as ps:
          r =  b._ingest_source(source, ps, clean_files)
  
      return r