code: def parent_site(self, site):
          
          # Avoid auto filter if site is already set.
          self._parent_site = site
  
          if settings.FLUENTCMS_EMAILTEMPLATES_ENABLE_CROSS_SITE:
              # Allow content to be shared between all sites:
              return self.filter(Q(parent_site=site) | Q(is_cross_site=True))
          else:
              return self.filter(parent_site=site)
docs: Filter to the given site, only give content relevant for that site.