docs: def stats(self):
          """
          Database usage statistics. Used by quota.
          """
          res = {}
          db = self._collection.database
          res['dbstats'] = db.command('dbstats')
          res['data'] = db.command('collstats', self._collection.name)
          res['totals'] = {'count': res['data']['count'],
                           'size': res['data']['size']
                           }
          return res