Create an instance of the named plugin and return it
        :param plugins_conf: dict of {alias: dict(plugin builder params) } 
        :type plugins_conf: dict
        :rtype: dict[str, AbstractPlugin]
        :return: dict of alias: plugin instance

def build_plugins(cls, plugins_conf):
        """Create an instance of the named plugin and return it
        :param plugins_conf: dict of {alias: dict(plugin builder params) } 
        :type plugins_conf: dict
        :rtype: dict[str, AbstractPlugin]
        :return: dict of alias: plugin instance
        """
        plugins = {}
        for alias, params_dict in plugins_conf.items():
            plugin_config = PluginConfig(**(params_dict.get('config') or {}))
            plugins[alias] = cls.build_plugin(class_name=params_dict['class_name'], config=plugin_config)
        return plugins