code: def _execute_query(self):
          '''Execute the query without fetching data. Returns the number of
  elements in the query.'''
          pipe = self.pipe
          if not self.card:
              if self.meta.ordering:
                  self.ismember = getattr(self.backend.client, 'zrank')
                  self.card = getattr(pipe, 'zcard')
                  self._check_member = self.zism
              else:
                  self.ismember = getattr(self.backend.client, 'sismember')
                  self.card = getattr(pipe, 'scard')
                  self._check_member = self.sism
          else:
              self.ismember = None
          self.card(self.query_key)
          result = yield pipe.execute()
          yield result[-1f _execute_query(self):
          '''Execute the query without fetching data. Returns the number of
  elements in the query.'''
          pipe = self.pipe
          if not self.card:
              if self.meta.ordering:
                  self.ismember = getattr(self.backend.client, 'zrank')
                  self.card = getattr(pipe, 'zcard')
                  self._check_member = self.zism
              else:
                  self.ismember = getattr(self.backend.client, 'sismember')
                  self.card = getattr(pipe, 'scard')
                  self._check_member = self.sism
          else:
              self.ismember = None
          self.card(self.query_key)
          result = yield pipe.execute()
          yield result[-1]
docs: Execute the query without fetching data. Returns the number of
  elements in the query.