code: def test_covariances_coherence_error(rndstate):
      """Test coherence error"""
      n_channels, n_times = 3, 50
      x = rndstate.randn(n_channels, n_times)
      with pytest.raises(ValueError):  # unknown coh
          coherence(x, coh="foobar")
  
imports: from numpy.testing import assert_array_almost_equal
  import numpy
  from scipy.linalg import block_diag
  from scipy.signal import welch, csd, coherence
  from sklearn.covariance import empirical_covariance
  import pytest
  from pyriemann.utils.covariance import covariances, covariances_EP, covariances_X, eegtocov, cross_spectrum, cospectrum, coherence, normalize, get_nondiag_weight, block_covariances, _complex_estimator
  from pyriemann.utils.test import is_real, is_hermitian, is_sym_pos_def, is_herm_pos_def
label_desc: Use image node_id 14 for calling a global function with example usage: test_covariances_coherence_error(rndstate) without return types