code: def invalidate_cache(self, obj=None, queryset=None,
                           extra=None, force_all=False):
          
  
          if self.cache_manager:
              if queryset != None:
                  force_all = True
  
              self.cache_manager.invalidate_cache(self.model, instance=obj,
                                                     extra=extra,
                                                     force_all=force_all)
docs: Method that should be called by all tiggers to invalidate the
          cache for an item(s).
  
          Should be overriden by inheriting classes to customize behavior.