code: def _check_backend(self, backend):
      if backend is None:
          raise ModuleNotFoundError(
              "No available audio backends in" " your environment."
          )
      if self.backends.get(backend, None) is None:
          raise ValueError(
              "{} is not found in your environment.".format(backend)
          )
  
file_path: nnabla/python/src/nnabla/utils/audio_utils/backend_manager.py
imports: import importlib
  from collections import OrderedDict
label_desc: Use image node_id 4 for calling the AudioUtilsBackendManager obj's underlying member method code with example usage: obj._check_backend(backend) without return types