code: def test_mean_nan_riemann_errors(get_mats):
      """Test the Riemannian NaN-mean errors"""
      n_matrices, n_channels = 5, 4
      mats = get_mats(n_matrices, n_channels, "spd")
  
      with pytest.raises(ValueError):  # not symmetric NaN values
          mats_ = mats.copy()
          mats_[
              0, 0
          ] = np.nan  # corrup only a row, not its corresp column
          nanmean_riemann(mats_)
      with pytest.raises(ValueError):  # not rows and columns NaN values
          mats_ = mats.copy()
          mats_[1, 0, 1] = np.nan  # corrup an off-diagonal value
          nanmean_riemann(mats_)
  
imports: import numpy
  from scipy.stats import gmean
  import pytest
  from pytest import approx
  from pyriemann.utils.geodesic import geodesic_riemann
  from pyriemann.utils.mean import mean_covariance, mean_ale, mean_alm, mean_euclid, mean_harmonic, mean_identity, mean_kullback_sym, mean_logdet, mean_logeuclid, mean_power, mean_riemann, mean_wasserstein, maskedmean_riemann, nanmean_riemann
label_desc: Use image node_id 17 for calling a global function with example usage: test_mean_nan_riemann_errors(get_mats) without return types