code: def _angle_between_each(A):
      """Measure the angle between each row vector in a matrix."""
      assert A.ndim == 2
      A = A / np.linalg.norm(A, axis=1, keepdims=True)
      d = (A @ A.T).ravel()
      np.clip(d, -1, 1, out=d)
      ang = np.abs(np.arccos(d))
      return ang
  
file_path: mne-python/mne/preprocessing/tests/test_hfc.py
imports: from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose
  from scipy.io import loadmat
  from mne._fiff.pick import pick_channels, pick_info, pick_types
  from mne.datasets import testing
  from mne.io import read_info, read_raw_fil
  from mne.preprocessing.hfc import compute_proj_hfc
label_desc: Use image node_id 2 for calling a global function with example usage: _angle_between_each(A) and returns: ang