code: def get_model_spec_ting(atomic_number):
      
      DATA_DIR = "/Users/annaho/Data/LAMOST/Mass_And_Age"
      temp = np.load("%s/X_u_template_KGh_res=1800.npz" %DATA_DIR)
      X_u_template = temp["X_u_template"]
      wl = temp["wavelength"]
      grad_spec = X_u_template[:,atomic_number]
      return wl, grad_spec
docs: X_u_template[0:2] are teff, logg, vturb in km/s
      X_u_template[:,3] -> onward, put atomic number 
      atomic_number is 6 for C, 7 for N