code: def test_sfm_sklearnlinearsolver():
      class SillySolver(opt.SKLearnLinearSolver):
          def fit(self, X, y):
              self.coef_ = np.ones(X.shape[-1])
  
      class EvenSillierSolver:
          def fit(self, X, y):
              self.coef_ = np.ones(X.shape[-1])
  
      fdata, fbvals, fbvecs = dpd.get_fnames()
      gtab = grad.gradient_table(fbvals, fbvecs)
      sfmodel = sfm.SparseFascicleModel(gtab, solver=SillySolver())
  
      npt.assert_(isinstance(sfmodel.solver, SillySolver))
      npt.assert_raises(
          ValueError,
          sfm.SparseFascicleModel,
          gtab,
          solver=EvenSillierSolver(),
      )
  
file_path: dipy/dipy/reconst/tests/test_sfm.py
imports: import warnings
  import numpy
  import numpy.testing
  import pytest
  import dipy.reconst.sfm
  import dipy.data
  import dipy.core.gradients
  import dipy.sims.voxel
  import dipy.core.optimize
  import dipy.reconst.cross_validation
  from dipy.io.gradients import read_bvals_bvecs
  from dipy.io.image import load_nifti_data
  from dipy.utils.optpkg import optional_package
label_desc: Use image node_id 6 for calling a global function with example usage: test_sfm_sklearnlinearsolver() without return types