code: def lm_deltat(freqs, damping_times, modes):
      
  
      dt = {}
      for lmn in modes:
          l, m, nmodes = int(lmn[0]), int(lmn[1]), int(lmn[2])
          for n in range(nmodes):
              dt['%d%d%d' %(l,m,n)] = 1. / qnm_freq_decay(freqs['%d%d%d' %(l,m,n)],
                                         damping_times['%d%d%d' %(l,m,n)], 1./1000)
  
      delta_t = min(dt.values())
      if delta_t < min_dt:
          delta_t = min_dt
  
      return delta_t
docs: Return the minimum delta_t of all the modes given, with delta_t given by
      the inverse of the frequency at which the amplitude of the ringdown falls to
      1/1000 of the peak amplitude.