code: def _extract_knob_feature_index(args):
      """extract knob feature for an index in extract_space"""
      config = _extract_space.get(args)
  
      return config.get_flatten_feature()
  
imports: import logging
  import time
  from typing import Dict
  import numpy
  from tvm.contrib.popen_pool import PopenPoolExecutor, StatusKind
  from ..None import feature
  from ..utils import get_rank
  from .metric import cover_curve, max_curve, recall_curve
  from .model_based_tuner import CostModel, FeatureCache
label_desc: Use image node_id 4 for calling a global function with example usage: _extract_knob_feature_index(args) and returns: config