code: def center_and_norm(x, axis=-1):
      """Center and norm x in place.
  
      Parameters
      ----------
      x: ndarray
          Array with an axis of observations (statistical units) measured on
          random variables.
      axis: int, optional
          Axis along which the mean and variance are calculated.
      """
      x = np.rollaxis(x, axis)
      x -= x.mean(axis=0)
      x /= x.std(axis=0)
  
file_path: mne-python/mne/preprocessing/tests/test_infomax.py
imports: import numpy
  import pytest
  from numpy.testing import assert_almost_equal
  from scipy import linalg, stats
  from mne.preprocessing.infomax_ import infomax
label_desc: Use image node_id 1 for calling a global function with example usage: center_and_norm(x, axis) without return types