class_docstr: PglLinkPropPredDataset
      
docstr: pre_process downlaoding data
          
docstr_tok: ["pre_process","downlaoding","data"]
code: def pre_process(self):
      """pre_process downlaoding data"""
      processed_dir = osp.join(self.root, "processed")
      pre_processed_file_path = osp.join(
          processed_dir, "pgl_data_processed"
      )
  
      if osp.exists(pre_processed_file_path):
          # TODO: Reload Preprocess files
          pass
      else:
          ### check download
          if not osp.exists(osp.join(self.root, "raw", "edge.csv.gz")):
              url = self.meta_info[self.name]["url"]
              if decide_download(url):
                  path = download_url(url, self.original_root)
                  extract_zip(path, self.original_root)
                  os.unlink(path)
                  # delete folder if there exists
                  try:
                      shutil.rmtree(self.root)
                  except:
                      pass
                  shutil.move(
                      osp.join(self.original_root, self.download_name),
                      self.root,
                  )
              else:
                  print("Stop download.")
                  exit(-1)
  
          raw_dir = osp.join(self.root, "raw")
  
          ### pre-process and save
          add_inverse_edge = to_bool(
              self.meta_info[self.name]["add_inverse_edge"]
          )
          self.graph = read_csv_graph_pgl(
              raw_dir, add_inverse_edge=add_inverse_edge
          )
  
file_path: PGL/legacy/pgl/contrib/ogb/linkproppred/dataset_pgl.py
imports: import pandas
  import shutil, os
  import os.path
  import numpy
  from ogb.utils.url import decide_download, download_url, extract_zip
  from ogb.linkproppred import make_master_file
  from pgl.contrib.ogb.io.read_graph_pgl import read_csv_graph_pgl
label_desc: Use image node_id 2 for calling the PglLinkPropPredDataset obj's underlying member method code with example usage: obj.pre_process() without return types