code: def test_is_spd_with_symmetrical_matrix():
      # matrix with negative eigenvalue
      matrix = np.array([[0, 1], [1, 0]])
      assert not is_spd(matrix, verbose=0)
  
      # matrix with 0 eigenvalue
      matrix = np.arange(4).reshape(2, 2)
      assert not is_spd(matrix, verbose=0)
  
      # spd matrix
      matrix = np.array([[2, 1], [1, 1]])
      assert is_spd(matrix, verbose=0)
  
imports: import numpy
  from nilearn._utils.extmath import fast_abs_percentile, is_spd
label_desc: Use image node_id 3 for calling a global function with example usage: test_is_spd_with_symmetrical_matrix() without return types