MasterPress 1.3.1 is a compatibility release for PHP 8 and WordPress 5.7. It still remains backwards compatible with older PHP versions.
MPFT_RelatedPost :: posts( Array / String $args )
Retrieves a collection of the posts selected in the field UI.
Note: you can further clarify the selected posts by setting the args parameter to a wp_parse_args compatible array or string.
Array / String $args
Either a string or array of query arguments as accepted by WordPress’ get_posts method.
Note that this method will ALWAYS override the post__in argument, since technically it infers the IDs of the selected posts first, and uses post__in to return them.