docstr: Length of the dataset
  Returns
  -------
  int
      Length of Dataset
docstr_tok: ["Length","of","the","dataset","Returns","--","--","--","-","int","Length","of","Dataset"]
code: def __len__(self):
      """Length of the dataset
      Returns
      -------
      int
          Length of Dataset
      """
      return len(self.graphs)
  
imports: from typing import Optional, Union, Dict
  import os
  import os.path
  import shutil
  from ogb.utils import smiles2graph
  from ogb.utils.url import decide_download, download_url, extract_zip
  import pandas
  import numpy
  from tqdm.auto import tqdm
  import torch
label_desc: Use image node_id 7 for calling the PCQM4Mv2Dataset obj's underlying member method code with example usage: obj.__len__() and returns: len