code: def test_invsqrtm():
      """Test matrix inverse square root"""
      C = 2 * np.eye(n_channels)
      Ctrue = (1.0 / np.sqrt(2)) * np.eye(n_channels)
      assert_array_almost_equal(invsqrtm(C), Ctrue, decimal=10)
  
file_path: pyRiemann/tests/test_utils_base.py
imports: import pytest
  import numpy
  from numpy.testing import assert_array_almost_equal
  from pyriemann.utils.base import expm, invsqrtm, logm, powm, sqrtm, nearest_sym_pos_def
  from pyriemann.utils.mean import mean_riemann
  from pyriemann.utils.test import is_pos_def, is_sym_pos_def
label_desc: Use image node_id 2 for calling a global function with example usage: test_invsqrtm() without return types