code: def frozen_bn_stats(model):
      """
      Set all the bn layers to eval mode.
      Args:
          model (model): model to set bn layers to eval mode.
      """
      for m in model.modules():
          if isinstance(m, nn.BatchNorm3d):
              m.eval()
  
imports: import json
  import logging
  import math
  import numpy
  import os
  from datetime import datetime
  import psutil
  import torch
  import torchvision.io
  from fvcore.nn.activation_count import activation_count
  from fvcore.nn.flop_count import flop_count
  from matplotlib import pyplot
  from torch import nn
  from torchvision.utils import make_grid
  import slowfast.utils.logging
  import slowfast.utils.multiprocessing
  from slowfast.datasets.utils import pack_pathway_output
  from slowfast.models.batchnorm_helper import SubBatchNorm3d
  from slowfast.utils.env import pathmgr
label_desc: Use image node_id 12 for calling a global function with example usage: frozen_bn_stats(model) without return types