class_docstr: DataLoader wrapper with slightly improved speed by not respawning worker
  processes at every epoch.
class_docstr_tok: ["DataLoader","wrapper","with","slightly","improved","speed","by","not","respawning","worker","processes","at","every","epoch","."]
code: def __len__(self):
      return self._length
  
file_path: dowhy/dowhy/causal_prediction/dataloaders/fast_data_loader.py
imports: import torch
label_desc: Use image node_id 3 for calling the FastDataLoader obj's underlying member method code with example usage: obj.__len__() and returns: self