new_contents: from pyscf.pbc.gto import Cell
  from pyscf.pbc.scf import KRHF
  from pyscf.pbc.tdscf.krhf_slow import TDRHF
  from pyscf.pbc.gw import KRGW
  
  cell = Cell()
  cell.atom = '''
  C 0.000000000000   0.000000000000   0.000000000000
  C 1.67   1.68   1.69
  '''
  cell.basis = {'C': [[0, (0.8, 1.0)],
                      [1, (1.0, 1.0)]]}
  cell.pseudo = 'gth-pade'
  cell.a = '''
  0.000000000, 3.370137329, 3.370137329
  3.370137329, 0.000000000, 3.370137329
  3.370137329, 3.370137329, 0.000000000'''
  cell.unit = 'B'
  cell.verbose = 7
  cell.build()
  
  model = KRHF(cell, cell.make_kpts([2, 1, 1]))
  model.kernel()
  
  model_td = TDRHF(model)
  model_td.kernel()
  
  model_gw = KRGW(model_td)
  model_gw.kernel()
  
  print model_gw.mo_energy
  
subject: Add a GW example