code: def test_erp_covariances_classes(n_classes, rndstate, get_labels):
      n_matrices, n_channels, n_times = 3 * n_classes, 3, 100
      x = rndstate.randn(n_matrices, n_channels, n_times)
      labels = get_labels(n_matrices, n_classes)
      cov = ERPCovariances(classes=[0])
      covmats = cov.fit_transform(x, labels)
      assert covmats.shape == (
          n_matrices,
          2 * n_channels,
          2 * n_channels,
      )
      assert is_spsd(covmats)
  
imports: import numpy
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_raises
  import pytest
  from pyriemann.estimation import Covariances, ERPCovariances, XdawnCovariances, CospCovariances, HankelCovariances, Coherences, Shrinkage, BlockCovariances, Kernels
  from pyriemann.utils.test import is_sym_pos_def, is_sym_pos_semi_def
label_desc: Use image node_id 5 for calling a global function with example usage: test_erp_covariances_classes(n_classes, rndstate, get_labels) without return types