code: def _extra_stats(self):
          
          return ['loglr'] + \
                 ['{}_optimal_snrsq'.format(det) for det in self._data] + \
                 ['{}_matchedfilter_snrsq'.format(det) for det in self._data]
docs: Adds ``loglr``, ``optimal_snrsq`` and matched filter snrsq in each
          detector to the default stats.