code: def _get_ref_batch(self, k=None):
      return next(iter(self.ref_sampler))[0].float()
  
imports: import functools
  import operator
  import torch
  from torch.autograd import grad
  from torch.utils.data import DataLoader
label_desc: Use image node_id 2 for calling the AttributionPriorExplainer obj's underlying member method code with example usage: obj._get_ref_batch(k) and returns: next