code: def _get_hit_count(self, database, enquire):
          
          return self._get_enquire_mset(
              database, enquire, 0, database.get_doccount()
          ).size()
docs: Given a database and enquire instance, returns the estimated number
          of matches.
  
          Required arguments:
              `database` -- The database to be queried
              `enquire` -- The enquire instance