code: def extract_year(index):
      """Return year of time index entry, normalized"""
      return (index.year - 1950) / 50
  
imports: import copy
  from datetime import date, timedelta
  import matplotlib.pyplot
  import numpy
  import pandas
  import pytest
  import shap
  import sklearn
  from dateutil.relativedelta import relativedelta
  from numpy.testing import assert_array_equal
  from sklearn.preprocessing import MinMaxScaler
  from darts import TimeSeries
  from darts.dataprocessing.transformers import Scaler
  from darts.explainability.explainability_result import ShapExplainabilityResult
  from darts.explainability.shap_explainer import MIN_BACKGROUND_SAMPLE, ShapExplainer
  from darts.models import CatBoostModel, ExponentialSmoothing, LightGBMModel, LinearRegressionModel, NotImportedModule, RegressionModel, XGBModel
  from darts.utils.timeseries_generation import linear_timeseries
label_desc: Use image node_id 1 for calling a global function with example usage: extract_year(index) and returns: unknown