code: def get_tau_at_quantile(mean, stddev, quantile):
      
      tau_model = {}
      for imt in mean:
          tau_model[imt] = {}
          for key in mean[imt]:
              if quantile is None:
                  tau_model[imt][key] = mean[imt][key]
              else:
                  tau_model[imt][key] = _at_percentile(mean[imt][key],
                                                       stddev[imt][key],
                                                       quantile)
      return tau_model
docs: Returns the value of tau at a given quantile in the form of a dictionary
      organised by intensity measure