code: def model_cache_key(self, model, key, cache_key):
      if cache_key and key:
          return f"{cache_key}_key={key}"
      elif cache_key and not key:
          return cache_key
      elif key is None:
          return model
      else:
          f"{model}_key={key}"
  
imports: from collections import OrderedDict
  import gc
  import logging
  import functools
  import psutil
  from finetune.target_models.sequence_labeling import SequenceLabeler
  import tensorflow
  from finetune.base import BaseModel
  from finetune.custom_ops import BytesInUse, BytesLimit, MaxBytesInUse
  from finetune.errors import FinetuneSchedulerError
label_desc: Use image node_id 4 for calling the Scheduler obj's underlying member method code with example usage: obj.model_cache_key(model, key, cache_key) and returns: cache_key, str, key, cache_key, model