code: def get_callback_version():
      callback = _get_callback("get_callback_version")
      if callback:
          return callback.get_callback_version()
      else:
          return None
  
file_path: nnabla/python/src/nnabla/utils/callback.py
imports: from nnabla.config import nnabla_config
  import importlib
label_desc: Use image node_id 3 for calling a global function with example usage: get_callback_version() and returns: callback, None