code: def normalize(self, x):
      return (x - self.mean) / self.std
  
imports: import numpy
  from keras.models import model_from_config, Sequential, Model, model_from_config
  import keras.optimizers
  import keras.backend
label_desc: Use image node_id 2 for calling the WhiteningNormalizer obj's underlying member method code with example usage: obj.normalize(x) and returns: unknown