code: def get_allowed_plugins(self, placeholder_slot):
          
          # See if there is a limit imposed.
          slot_config = appsettings.FLUENT_CONTENTS_PLACEHOLDER_CONFIG.get(placeholder_slot) or {}
          plugins = slot_config.get('plugins')
          if not plugins:
              return self.get_plugins()
          else:
              try:
                  return self.get_plugins_by_name(*plugins)
              except PluginNotFound as e:
                  raise PluginNotFound(str(e) + " Update the plugin list of the FLUENT_CONTENTS_PLACEHOLDER_CONFIG['{0}'] setting.".format(placeholder_slot))
docs: Return the plugins which are supported in the given placeholder name.