code: def cbpdnmd_relax(k):
      
  
      mp_Z_X[k] = mp_xrlx * mp_Z_X[k] + (1 - mp_xrlx) * mp_Z_Y1[k]
      mp_DX[k] = mp_xrlx * mp_DX[k] + (1 - mp_xrlx) * (mp_Z_Y0[k] + mp_S[k])
docs: Do relaxation for the cbpdn stage. The only parameter is the slice
      index `k` and there are no return values; all inputs and outputs are
      from and to global variables.