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.

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)