jamierumbelow MY_Model：选择db不起作用

I'm using the fantastic MY_Model of Jamie Rumbelow, it's very fast and easy to use on the default db configuration. But when I want to use a secondary configuration the problems cames out.

As the reference suggest, I added in the model

public $_db_group = 'db_config_name';

But when I execute any command, the result is:

Error Number: 1146
Table 'DEFAULT_db_name.table_name' doesn't exist
SELECT * FROM (`table_name`)

I'm doing something wrong?

in your model you have to define $_db_group as public

public $_db_group = 'group_name';

check the model doc