code: def norm_spec(self, x):
      return (x - self.spec_min) / (
          self.spec_max - self.spec_min
      ) * 2 - 1
  
imports: import os
  from collections import deque
  import librosa
  import numpy
  import onnxruntime
  from pypinyin import lazy_pinyin
  from tqdm import tqdm
  from .inference.svs.opencpop.map import cpop_pinyin2ph_func
  from .utils.hparams import hparams
  from .utils.text_encoder import TokenTextEncoder
label_desc: Use image node_id 3 for calling the Infer obj's underlying member method code with example usage: obj.norm_spec(x) and returns: unknown