code: def test_flatchannelremover(rndstate):
      n_matrices, n_channels, n_times = 10, 3, 100
      X = rndstate.rand(n_times, n_matrices, n_channels)
      X[:, 0, :] = 999
      fcr = FlatChannelRemover()
      fcr.fit(X)
      assert_array_equal(fcr.channels_, range(1, 10))
      Xt = fcr.fit_transform(X)
      assert_array_equal(Xt, X[:, 1:, :])
  
imports: from numpy.testing import assert_array_equal
  from pyriemann.channelselection import ElectrodeSelection, FlatChannelRemover
label_desc: Use image node_id 3 for calling a global function with example usage: test_flatchannelremover(rndstate) without return types