class_docstr: Cache for model outputs.
code: def get(self, key: CacheKey) -> Optional[Any]:
      return self._d.get(key) if key is not None else None
  
imports: from collections.abc import Callable, Iterable
  import os
  import pickle
  import threading
  from typing import Any, Optional, Union
  from absl import logging
  from lit_nlp.api import dataset
  from lit_nlp.api import model
  from lit_nlp.api import types
  from lit_nlp.lib import serialize
label_desc: Use image node_id 4 for calling the PredsCache obj's underlying member method code with example usage: obj.get(key) and returns: unknown