class_docstr: PglGraphPropPredDataset
docstr: Pre-processing
docstr_tok: ["Pre-processing"]
code: def pre_process(self):
      """Pre-processing"""
      processed_dir = osp.join(self.root, "processed")
      raw_dir = osp.join(self.root, "raw")
      pre_processed_file_path = osp.join(
          processed_dir, "pgl_data_processed"
      )
  
      if os.path.exists(pre_processed_file_path):
          # TODO: Load Preprocessed
          pass
      else:
          ### download
          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)
  
          ### preprocess
          add_inverse_edge = to_bool(
              self.meta_info[self.name]["add_inverse_edge"]
          )
          self.graphs = read_csv_graph_pgl(
              raw_dir, add_inverse_edge=add_inverse_edge
          )
          self.graphs = np.array(self.graphs)
          self.labels = np.array(
              pd.read_csv(
                  osp.join(raw_dir, "graph-label.csv.gz"),
                  compression="gzip",
                  header=None,
              ).values
          )
  
file_path: PGL/legacy/pgl/contrib/ogb/graphproppred/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.graphproppred 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 PglGraphPropPredDataset obj's underlying member method code with example usage: obj.pre_process() without return types