code: def test_svc_cref_error(get_mats, get_targets, metric):
      n_matrices, n_channels = 6, 3
      covmats = get_mats(n_matrices, n_channels, "spd")
      targets = get_targets(n_matrices)
  
      def Cref(X, met):
          mean_covariance(X, metric=met)
  
      with pytest.raises(TypeError):
          SVR(Cref=Cref).fit(covmats, targets)
  
      Cref = metric
  
      with pytest.raises(TypeError):
          SVR(Cref=Cref).fit(covmats, targets)
  
imports: import pickle
  import numpy
  from numpy.testing import assert_array_equal
  import pytest
  from conftest import get_distances, get_means, get_metrics
  from pyriemann.regression import SVR, KNearestNeighborRegressor
  from pyriemann.utils.kernel import kernel
  from pyriemann.utils.mean import mean_covariance
label_desc: Use image node_id 11 for calling a global function with example usage: test_svc_cref_error(get_mats, get_targets, metric) without return types