code: def test_electrodeselection_nonelabel(get_mats):
      n_matrices, n_channels = 1, 3
      covmats, labels = get_mats(n_matrices, n_channels, "spd"), None
      se = ElectrodeSelection()
      se.fit(covmats, labels)
      se.transform(covmats)
  
imports: from numpy.testing import assert_array_equal
  from pyriemann.channelselection import ElectrodeSelection, FlatChannelRemover
label_desc: Use image node_id 2 for calling a global function with example usage: test_electrodeselection_nonelabel(get_mats) without return types