code: def applicable_models(self):
          
          Page        = apps.get_model('wagtailcore', 'Page')
          applicable  = []
  
          for model in apps.get_models():
              meta    = getattr(model, '_meta')
              fields  = meta.get_all_field_names()
  
              if issubclass(model, Page) and 'tags' in fields:
                  applicable.append(model)
  
          return applicable
docs: Returns a list of model classes that subclass Page
          and include a "tags" field.
  
          :rtype: list.