new_contents: #!/usr/bin/env python
  
  '''
  FNO-CCSD for RHF and UHF
  '''
  
  from pyscf import gto, scf, cc
  
  mol = gto.Mole()
  mol.atom = [
      ['O' , (0. , 0.     , 0.)],
      ['H' , (0. , -0.757 , 0.587)],
      ['H' , (0. , 0.757  , 0.587)]]
  
  mol.basis = 'cc-pvqz'
  mol.build()
  
  mf = scf.RHF(mol).run()
  mycc = cc.CCSD(mf).run()
  print(mycc.e_corr - -0.3170511898840137)
  
  mycc = cc.FNOCCSD(mf).run()
  print(mycc.e_corr - -0.3170419015445936)
  
  # lower NO occupation threshold
  mycc = cc.FNOCCSD(mf, thresh=1e-5).run()
  print("error from canonical =", mycc.e_corr - -0.3170511898840137)
  
  # use delta-MP2 as correction
  print("error from canonical =", mycc.e_corr+mycc.delta_emp2 - -0.3170511898840137)
  
subject: Add FNO-CCSD example