'Filter based on the kwargs given, uses django orm like syntax
**Example** ::
# filter between 100 and 200
feed = feed.filter(activity_id__gte=100)
feed = feed.filter(activity_id__lte=200)
# the same statement but in one step
feed = feed.filter(activity_id__gte=100, activity_id__lte=200)'

def filter(self, **kwargs):

    new = self._clone()
    new._filter_kwargs.update(kwargs)
    return new
