class_docstr: BaseDataset for PGLBox.
      
docstr: This is a thread to fill the dataset_list
          
docstr_tok: ["This","is","a","thread","to","fill","the","dataset_list"]
code: def preload_thread(self, dataset_list):
      """This is a thread to fill the dataset_list"""
      try:
          self.preload_worker(dataset_list)
      except Exception as e:
          self.could_load_sem.release()
          self.ins_ready_sem.release()
          log.warning("preload_thread exception :%s" % (e))
          log.warning(
              "preload_thread traceback :%s" % (traceback.format_exc())
          )
  
imports: import os
  import time
  import threading
  import traceback
  import numpy
  import paddle
  from paddle.distributed import fleet
  import paddle.fluid
  from pgl.utils.logger import log
  import util
  import helper
  from place import get_cuda_places
  import models.model_util
label_desc: Use image node_id 6 for calling the BaseDataset obj's underlying member method code with example usage: obj.preload_thread(dataset_list) without return types