code: def test_detrend_linear(self):
      # 0D.
      assert mlab.detrend_linear(0.0) == 0.0
      assert mlab.detrend_linear(5.5) == 0.0
      assert mlab.detrend(5.5, key="linear") == 0.0
      assert mlab.detrend(5.5, key=mlab.detrend_linear) == 0.0
      for sig in [  # 1D.
          self.sig_off,
          self.sig_slope,
          self.sig_slope + self.sig_off,
      ]:
          self.allclose(mlab.detrend_linear(sig), self.sig_zeros)
  
imports: from numpy.testing import assert_allclose, assert_almost_equal, assert_array_equal, assert_array_almost_equal_nulp
  import numpy
  import pytest
  from matplotlib import mlab
label_desc: Use image node_id 9 for calling the TestDetrend obj's underlying member method code with example usage: obj.test_detrend_linear() without return types