class_docstr: A placeholder class for unavailable context managers
  
  This context manager will return a value which will throw an
  UnavailableError if used in any way, but the context manager itself can be
  safely invoked.
class_docstr_tok: ["A","placeholder","class","for","unavailable","context","managers","This","context","manager","will","return","a","value","which","will","throw","an","UnavailableError","if","used","in","any","way",",","but","the","context","manager","itself","can","be","safely","invoked","."]
code: def __exit__(self, *args, **kwargs):
      pass
  
imports: import importlib
  import traceback
  from contextlib import contextmanager
  from cuml.internals.device_support import CPU_ENABLED, GPU_ENABLED
  from cuml.internals import logger
label_desc: Use image node_id 3 for calling the UnavailableNullContext obj's underlying member method code with example usage: obj.__exit__() without return types