code: def test_theta_0():
      # with theta = 0
      y = load_airline()
      t = ThetaLinesTransformer(0)
      t.fit(y)
      actual = t.transform(y)
      x = np.arange(y.size) + 1
      lin_regress = linregress(x, y)
      expected = lin_regress.intercept + lin_regress.slope * x
  
      np.testing.assert_almost_equal(actual, expected, decimal=8)
  
imports: import numpy
  import pytest
  from scipy.stats import linregress
  from sktime.datasets import load_airline
  from sktime.transformations.series.theta import ThetaLinesTransformer
label_desc: Use image node_id 1 for calling a global function with example usage: test_theta_0() without return types