code: def calc_z(bands, filling, interaction, hund_cu, name):
      
  
      while True:
          try:
              data = np.load(name+'.npz')
              break
          except IOError:
              dopout = []
              for dop in filling:
                  slsp = Spinon(slaves=2*bands, orbitals=bands, \
                               hopping=[0.5]*2*bands, populations=[dop]*2*bands)
                  dopout.append(solve_loop(slsp, interaction, hund_cu)[0][0])
              np.savez(name, zeta=dopout, u_int=interaction, doping=filling, hund=hund_cu)
  
      return data
docs: Calculates the quasiparticle weight of degenerate system of N-bands
         at a given filling within an interaction range and saves the file