code: def test_diagonality(data):
      # basis_projections are diagonal, whether standardized or not
      p = pca(data["fmridata"], -1)  # standardized
      assert diagonal_covariance(p["basis_projections"], -1)
      pns = pca(data["fmridata"], -1, standardize=False)  # not
      assert diagonal_covariance(pns["basis_projections"], -1)
  
imports: import numpy
  import pytest
  from nipy.io.api import load_image
  from nipy.testing import assert_almost_equal, assert_array_almost_equal, funcfile
  from ..pca import pca
label_desc: Use image node_id 9 for calling a global function with example usage: test_diagonality(data) without return types