code: def fetch_size(self, v):
          
  
          if not isinstance(v, six.integer_types):
              raise TypeError
          if v == self._fetch_size:
              return self
  
          if v < 1:
              raise QueryException("fetch size less than 1 is not allowed")
  
          clone = copy.deepcopy(self)
          clone._fetch_size = v
          return clone
docs: Sets the number of rows that are fetched at a time.
  
          *Note that driver's default fetch size is 5000.*
  
          .. code-block:: python
  
              for user in User.objects().fetch_size(500):
                  print(user)