code: def _get_feature_extractor(model_name):
      global VGGish_instance
      assert model_name == "VGGish"
      if VGGish_instance is None:
          VGGish_instance = VGGishFeatureExtractor()
      return VGGish_instance
  
file_path: turicreate/src/python/turicreate/toolkits/sound_classifier/_audio_feature_extractor.py
imports: import time
  import numpy
  import turicreate.toolkits._tf_utils
  import turicreate
  from .vggish_params import SAMPLE_RATE
  from .._internal_utils import _mac_ver
  from .._pre_trained_models import VGGish
  from turicreate._deps.minimal_package import _minimal_package_import_check
label_desc: Use image node_id 1 for calling a global function with example usage: _get_feature_extractor(model_name) and returns: VGGish_instance