class_docstr: The GraphSAINT random walk sampler class (see
  :class:`~torch_geometric.loader.GraphSAINTSampler`).
  
  Args:
      walk_length (int): The length of each random walk.
code: def _filename(self):
      return (
          f"{self.__class__.__name__.lower()}_{self.walk_length}_"
          f"{self.sample_coverage}.pt"
      )
  
imports: import os.path
  from typing import Optional
  import torch
  from tqdm import tqdm
  from torch_geometric.typing import SparseTensor
label_desc: Use image node_id 2 for calling the GraphSAINTRandomWalkSampler obj's underlying member method code with example usage: obj._filename() and returns: self, str, self, str, self, str