code: def _merge_categories_map(annotations: NestedDict) -> Dict[str, str]:
      """Some categories should be renamed into others.
  
      This code segment is based on the TAO provided preprocessing API.
  
      Args:
        annotations: a dictionary containing all the annotations
  
      Returns:
        merge_map: dictionary mapping from category id to merged id
      """
      merge_map = {}
      for category in annotations["categories"]:
          if "merged" in category:
              for to_merge in category["merged"]:
                  merge_map[to_merge["id"]] = category["id"]
      return merge_map
  
imports: from __future__ import annotations
  import collections
  import json
  import os
  from typing import Any, Dict, Optional, Tuple
  from etils import epath
  import numpy
  import tensorflow_datasets.public_api
label_desc: Use image node_id 2 for calling a global function with example usage: _merge_categories_map(annotations) and returns: merge_map