code: def _scale_y(y):
      """Normalize variance to 1."""
      return y / y.std()
  
imports: from typing import Dict, Hashable, List, Optional, Tuple, Union
  import networkx
  import numpy
  import pandas
  from sklearn.gaussian_process.kernels import RBF, Kernel
  from causalnex.structure import StructureModel
  from causalnex.structure.categorical_variable_mapper import VariableFeatureMapper, validate_schema
label_desc: Use image node_id 18 for calling a global function with example usage: _scale_y(y) and returns: unknown