class_docstr: A sampler that calls `posterior.rsample_from_base_samples` to
  generate the samples via index base samples.
docstr: Null operation just needed for compatibility with
  `CachedCholeskyAcquisitionFunction`.
code: def _update_base_samples(
      self, posterior: EnsemblePosterior, base_sampler: IndexSampler
  ) -> None:
      r"""Null operation just needed for compatibility with
      `CachedCholeskyAcquisitionFunction`."""
      pass
  
file_path: botorch/botorch/sampling/index_sampler.py
imports: from __future__ import annotations
  import torch
  from botorch.posteriors.ensemble import EnsemblePosterior
  from botorch.sampling.base import MCSampler
  from torch import Tensor
label_desc: Use image node_id 3 for calling the IndexSampler obj's underlying member method code with example usage: obj._update_base_samples(posterior, base_sampler) without return types