code: def source_file(self) -> List[str]:
      return self._source_file
  
imports: import argparse
  import itertools
  import json
  import logging
  import os
  import pickle
  import random
  import sys
  import time
  from collections import OrderedDict
  from typing import Iterable, List, Optional, Tuple
  import numpy
  import torch
  import torch.multiprocessing
  from reagent.ope.estimators.estimator import Evaluator
  from reagent.ope.estimators.slate_estimators import DCGSlateMetric, DMEstimator, DoublyRobustEstimator, ERRSlateMetric, IPSEstimator, LogSample, NDCGSlateMetric, PassThruDistribution, PBMEstimator, PseudoInverseEstimator, RankingDistribution, RewardDistribution, SlateContext, SlateEstimator, SlateEstimatorInput, SlateItemFeatures, SlateItemValues, SlateModel, SlateQuery, SlateSlots
  from reagent.ope.estimators.types import Trainer, TrainingData
  from reagent.ope.trainers.linear_trainers import DecisionTreeTrainer, LassoTrainer
  from reagent.ope.utils import Clamper
  from torch import Tensor
label_desc: Use image node_id 15 for calling the MSLRDatasets obj's underlying member method code with example usage: obj.source_file() and returns: self