code: def write_stilde(self, stilde_dict, group=None):
          
          subgroup = self.data_group + "/{ifo}/stilde"
          if group is None:
              group = subgroup
          else:
              group = '/'.join([group, subgroup])
          for ifo, stilde in stilde_dict.items():
              self[group.format(ifo=ifo)] = stilde
              self[group.format(ifo=ifo)].attrs['delta_f'] = stilde.delta_f
              self[group.format(ifo=ifo)].attrs['epoch'] = float(stilde.epoch)
docs: Writes stilde for each IFO to file.
  
          Parameters
          -----------
          stilde : {dict, FrequencySeries}
              A dict of FrequencySeries where the key is the IFO.
          group : {None, str}
              The group to write the strain to. If None, will write to the top
              level.