docstr: :return: list of ndarray for weights
docstr_tok: [":","return",":","list","of","ndarray","for","weights"]
code: def _extract_trainable_values(self):
      """
      :return: list of ndarray for weights
      """
      return None
  
file_path: analytics-zoo/pyzoo/zoo/pipeline/api/onnx/mapper/operator_mapper.py
imports: import zoo.pipeline.api.keras.layers
  import zoo.pipeline.api.autograd
  from zoo.pipeline.api.onnx.onnx_helper import OnnxHelper
  import zoo.pipeline.api.onnx.mapper
  import importlib
  import numpy
label_desc: Use image node_id 7 for calling the OperatorMapper obj's underlying member method code with example usage: obj._extract_trainable_values() and returns: None