code: def parse_overrides(serialized_overrides):
      if serialized_overrides:
          ext_vars = dict(os.environ)
          return unflatten(
              json.loads(
                  evaluate_snippet(
                      "", serialized_overrides, ext_vars=ext_vars
                  )
              )
          )
      else:
          return {}
  
imports: from __future__ import with_statement
  from __future__ import absolute_import
  from collections import MutableMapping, OrderedDict
  import copy
  import json
  import logging
  import os
  from io import open
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.file_utils import cached_path
label_desc: Use image node_id 3 for calling a global function with example usage: parse_overrides(serialized_overrides) and returns: unflatten, dict