'Validate user\'s item filter config
:return: Nothing.
:rtype: None
:raise: ConfigException: When an item doesn\'t exist in ../../data/items.json'

def _validate_item_filter(self):

    item_list = json.load(open(os.path.join(_base_dir, 'data', 'items.json')))
    for (config_item_name, bag_count) in self.items_filter.iteritems():
        if (config_item_name not in item_list.viewvalues()):
            if (config_item_name not in item_list):
                raise ConfigException('item    {}    does    not    exist,    spelling    mistake?    (check    for    valid    item    names    in    data/items.json)'.format(config_item_name))
