code: def test_decorrelate(self, reset_randomstate):
      d = 30
      dg = np.linspace(1, 2, d)
      root = np.random.normal(size=(d, 4))
      fac = FactoredPSDMatrix(dg, root)
      mat = fac.to_matrix()
      rmat = np.linalg.cholesky(mat)
      dcr = fac.decorrelate(rmat)
      idm = np.dot(dcr, dcr.T)
      assert_almost_equal(idm, np.eye(d))
  
      rhs = np.random.normal(size=(d, 5))
      mat2 = np.dot(rhs.T, np.linalg.solve(mat, rhs))
      mat3 = fac.decorrelate(rhs)
      mat3 = np.dot(mat3.T, mat3)
      assert_almost_equal(mat2, mat3)
  
imports: import warnings
  import numpy
  from numpy.testing import assert_almost_equal, assert_allclose
  import scipy.sparse
  import pytest
  from statsmodels.stats.correlation_tools import corr_nearest, corr_clipped, cov_nearest, _project_correlation_factors, corr_nearest_factor, _spg_optim, corr_thresholded, cov_nearest_factor_homog, FactoredPSDMatrix
  from statsmodels.tools.testing import Holder
label_desc: Use image node_id 5 for calling the Test_Factor obj's underlying member method code with example usage: obj.test_decorrelate(reset_randomstate) without return types