* 'custom_some_group:my_field' => 'myinfo',
* // updates record ID 8 in my_other_field in multi-valued some_big_group
* 'custom_some_big_group:my_other_field:8' => 'myinfo',
* 'custom_some_group:my_field' => 'myinfo',
* // updates record ID 8 in my_other_field in multi-valued some_big_group
* 'custom_some_big_group:my_other_field:8' => 'myinfo',