code: def test_list_mean_centering():
      X2 = [1.0, 2.0, 3.0]
      X2_out = np.array([-1.0, 0.0, 1.0])
      mc = MeanCenterer()
      assert mc.fit_transform(X2).all().all() == X2_out.all()
  
imports: import numpy
  import pytest
  from mlxtend.preprocessing import MeanCenterer
label_desc: Use image node_id 3 for calling a global function with example usage: test_list_mean_centering() without return types