class_docstr: A base class for creating reference (aka baseline) tensor for a sequence of
  tokens. A typical example of such token is `PAD`. Users need to provide the
  index of the reference token in the vocabulary as an argument to
  `TokenReferenceBase` class.
code: def __init__(self, reference_token_idx: int = 0) -> None:
      self.reference_token_idx = reference_token_idx
  
file_path: captum/captum/attr/_models/base.py
imports: import warnings
  from functools import reduce
  import torch
  from torch.nn import Module
label_desc: Use image node_id 1 to create a new TokenReferenceBase object  with example: obj = TokenReferenceBase(reference_token_idx)