code: def test_block_covariances_est(estimator, rndstate):
      """Test BlockCovariances estimators"""
      n_matrices, n_channels, n_times = 2, 12, 100
      x = rndstate.randn(n_matrices, n_channels, n_times)
      cov = BlockCovariances(block_size=6, estimator=estimator)
      cov.fit(x)
      covmats = cov.fit_transform(x)
      assert cov.get_params() == dict(block_size=6, estimator=estimator)
      assert covmats.shape == (n_matrices, n_channels, n_channels)
      assert is_spd(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 9 for calling a global function with example usage: test_block_covariances_est(estimator, rndstate) without return types