docs: def solve_loop(slsp, u_span, j_coup):
      """Calculates the quasiparticle for the input loop of:
          @param slsp: Slave spin Object
          @param Uspan: local Couloumb interation
          @param J_coup: Fraction of Uspan of Hund coupling strength"""
  
      zet, lam, eps, hlog, mean_f = [], [], [], [], [None]
  
      for u in u_span:
          print(u, j_coup)
          hlog.append(slsp.selfconsistency(u, j_coup, mean_f[-1]))
          mean_f.append(slsp.mean_field())
          zet.append(slsp.quasiparticle_weight())
          lam.append(slsp.param['lambda'])
          eps.append(orbital_energies(slsp.param, zet[-1]))
  
      return np.asarray([zet, lam, eps]), hlog, mean_f