<https://metabox.io/support/topic/add-readonly-attribute-to-checkbox-list-items/#webpage>
<http://schema.org/description>
"Hi, How could I add a readonly attribute to checkbox list items if one them is checked. Ex: , ], If 'None' is checked, '1', '2', '3' have to be readonly."
<https://metabox.io/support/topic/add-readonly-attribute-to-checkbox-list-items/>