code: def test_mean(self):
      np.testing.assert_almost_equal(calc_mean(const0), 0.0)
      np.testing.assert_almost_equal(calc_mean(const1), 1.0)
      np.testing.assert_almost_equal(calc_mean(constNeg), -1.0)
      np.testing.assert_almost_equal(calc_mean(constF), 2.5)
      np.testing.assert_almost_equal(calc_mean(lin), 9.5)
      np.testing.assert_almost_equal(
          calc_mean(lin0), -3.552713678800501e-16, decimal=5
      )
      np.testing.assert_almost_equal(
          calc_mean(wave), 7.105427357601002e-18, decimal=5
      )
      np.testing.assert_almost_equal(
          calc_mean(offsetWave), 2.0, decimal=5
      )
      np.testing.assert_almost_equal(
          calc_mean(noiseWave), -0.0014556635615470554, decimal=5
      )
  
imports: import unittest
  import numpy
  from tsfel.feature_extraction.features import *
label_desc: Use image node_id 4 for calling the TestFeatures obj's underlying member method code with example usage: obj.test_mean() without return types