code: def _get_sz_change_idxs(sizes):
      "Get the indexes of the layers where the size of the activation changes."
      feature_szs = [size[-1] for size in sizes]
      sz_chg_idxs = list(
          np.where(
              np.array(feature_szs[:-1]) != np.array(feature_szs[1:])
          )[0]
      )
      return sz_chg_idxs
  
file_path: fastai/fastai/vision/models/unet.py
imports: from __future__ import annotations
  from ...torch_basics import *
  from ...callback.hook import *
label_desc: Use image node_id 1 for calling a global function with example usage: _get_sz_change_idxs(sizes) and returns: sz_chg_idxs