code: def test_kernel_x_y(ker, get_mats):
      """Test kernel for different X and Y"""
      n_matrices_X, n_matrices_Y, n_channels = 6, 5, 3
      X = get_mats(n_matrices_X, n_channels, "spd")
      Y = get_mats(n_matrices_Y, n_channels, "spd")
      K = kernel(X, Y, metric=ker)
      assert K.shape == (n_matrices_X, n_matrices_Y)
  
file_path: pyRiemann/tests/test_utils_kernel.py
imports: import numpy
  from numpy.testing import assert_array_equal, assert_array_almost_equal
  import pytest
  from pyriemann.utils.base import logm
  from pyriemann.utils.kernel import kernel, kernel_euclid, kernel_logeuclid, kernel_riemann
  from pyriemann.utils.mean import mean_covariance
  from pyriemann.utils.test import is_sym_pos_semi_def
label_desc: Use image node_id 3 for calling a global function with example usage: test_kernel_x_y(ker, get_mats) without return types