class_docstr: Dataset for Graph Isomorphism Network (GIN)
  Adapted from https://github.com/weihua916/powerful-gnns/blob/master/dataset.zip.
class_docstr_tok: ["Dataset","for","Graph","Isomorphism","Network","(","GIN",")","Adapted","from","https",":","\/\/github.com\/weihua916\/powerful-gnns\/blob\/master\/dataset.zip","."]
docstr: return the number of graphs
docstr_tok: ["return","the","number","of","graphs"]
code: def __len__(self):
      """return the number of graphs"""
      return len(self.graph_list)
  
imports: import os
  import sys
  import numpy
  from sklearn.model_selection import StratifiedKFold
  import pgl
  from pgl.utils.logger import log
label_desc: Use image node_id 2 for calling the GINDataset obj's underlying member method code with example usage: obj.__len__() and returns: len