class_docstr: A subset of the last.fm music website keeping track of users' listining
  information from various sources, as collected in the
  `"MAGNN: Metapath Aggregated Graph Neural Network for Heterogeneous Graph
  Embedding" <https://arxiv.org/abs/2002.01680>`_ paper.
  last.fm is a heterogeneous graph containing three types of entities - users
  (1,892 nodes), artists (17,632 nodes), and artist tags (1,088 nodes).
  This dataset can be used for link prediction, and no labels or features are
  provided.
  
  Args:
      root (str): Root directory where the dataset should be saved.
      transform (callable, optional): A function/transform that takes in an
          :obj:`torch_geometric.data.HeteroData` object and returns a
          transformed version. The data object will be transformed before
          every access. (default: :obj:`None`)
      pre_transform (callable, optional): A function/transform that takes in
          an :obj:`torch_geometric.data.HeteroData` object and returns a
          transformed version. The data object will be transformed before
          being saved to disk. (default: :obj:`None`)
      force_reload (bool, optional): Whether to re-process the dataset.
          (default: :obj:`False`)
code: def processed_file_names(self) -> str:
      return "data.pt"
  
file_path: pytorch_geometric/torch_geometric/datasets/last_fm.py
imports: import os
  import os.path
  from itertools import product
  from typing import Callable, List, Optional
  import numpy
  import scipy.sparse
  import torch
  from torch_geometric.data import HeteroData, InMemoryDataset, download_url, extract_zip
label_desc: Use image node_id 3 for calling the LastFM obj's underlying member method code with example usage: obj.processed_file_names() and returns: str