docs: def get_plugin(self, identifier, cls=None):
          """
          Return the plugin corresponding to the given identifier and type.
  
          Args:
              identifier (str): identifier of the plugin.
              cls (str): one of checker / provider.
  
          Returns:
              Checker/Provider: plugin class.
          """
          if ((cls is None or cls == 'provider')
                  and identifier in self.available_providers):
              return self.available_providers[identifier]
          elif ((cls is None or cls == 'checker')
                  and identifier in self.available_checkers):
              return self.available_checkers[identifier]
          return Config.load_local_plugin(identifier)