code: def test_mean_covariance_metric(metric, mean, get_mats):
      """Test mean_covariance for metric"""
      n_matrices, n_channels = 3, 3
      mats = get_mats(n_matrices, n_channels, "spd")
      C = mean_covariance(mats, metric=metric)
      Ctrue = mean(mats)
      assert np.all(C == Ctrue)
  
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 19 for calling a global function with example usage: test_mean_covariance_metric(metric, mean, get_mats) without return types