def METHOD_NAME(self):
    """
    List the plugins that are in the plugins directory
    :return: The set containing a list of plugin names
    :rtype: set
    """
    checks_in_config = self.config.items('passive checks')
    required_plugins = set()
    for target, check in checks_in_config:
        if '|' in target:
            if 'plugin/' in check:
                plugin_search = re.search(u'plugin/([^/]+).*', check)
                plugin_name = plugin_search.group(1)
                required_plugins.add(plugin_name)
    return required_plugins