Trouble with User Role to Post Relationship

Hi,

If you want to use one role subscriber, just use the argument role, like this

function your_prefix_function_name() {
    MB_Relationships_API::register( [
        'id'   => 'user-to-post',
        'from' => [
            'object_type' => 'user',
            'field'       => [
                'query_args' => [
                    'role' => 'subscriber'
                ],
            ],
        ],
        'to'   => 'post',
    ] );
}