code: def _nest_stack(list_of_nests, axis=0):
      """Convert a list of nests to a nest of stacked lists."""
      return tree.map_structure(
          lambda *ts: tf.stack(ts, axis=axis), *list_of_nests
      )
  
file_path: acme/acme/agents/tf/svg0_prior/utils.py
imports: import collections
  from typing import Tuple, Optional, Dict, Iterable
  from acme import types
  from acme.tf import utils
  import sonnet
  import tensorflow
  import tree
label_desc: Use image node_id 4 for calling a global function with example usage: _nest_stack(list_of_nests, axis) and returns: tree