code: def _persistent_id(obj):
      if isinstance(obj, AssetFinder):
          return AssetFinder.PERSISTENT_TOKEN
      if isinstance(obj, TradingEnvironment):
          return TradingEnvironment.PERSISTENT_TOKEN
      return None
  
file_path: catalyst/catalyst/utils/serialization_utils.py
imports: from six import BytesIO
  import pickle
  from functools import partial
  from catalyst.assets import AssetFinder
  from catalyst.finance.trading import TradingEnvironment
label_desc: Use image node_id 1 for calling a global function with example usage: _persistent_id(obj) and returns: None, AssetFinder, TradingEnvironment