code: def _is_valid(key):
      if key.startswith("_"):
          return False
  
      if key in RESERVED_CLASS or key in RESERVED_INSTANCE:
          return False
  
      return True
  
imports: import types
  import warnings
  from collections import OrderedDict
  from typing import Dict, List, Callable, Union, Tuple, Optional, Type, Set, Iterable, Any
  from .config_function import ConfigFunction
  from .config_item import ConfigItem
  from .eval_function import EvalFunction
  from .utils import Value
  from ...None import monit
label_desc: Use image node_id 2 for calling a global function with example usage: _is_valid(key) and returns: True, False, False