code: def y_series():
      return load_airline()
  
file_path: sktime/sktime/transformations/series/detrend/tests/test_detrend.py
imports: import numpy
  import pandas
  import pytest
  from sktime.datasets import load_airline
  from sktime.forecasting.trend import PolynomialTrendForecaster
  from sktime.forecasting.trend.tests.test_trend import get_expected_polynomial_coefs
  from sktime.transformations.series.detrend import Detrender
label_desc: Use image node_id 1 for calling a global function with example usage: y_series() and returns: load_airline