Limit the columns in junction table on a BelongsToMany association

having a problem here. So i have two tables, ‘Groups’ and ‘User’ and a ‘through’ table ‘GroupsMembers’ and what i need to do is limit the columns that i get. Mostly because i don’t need them and Users have another table (grades) associated which also has columns irrelevants to me.

I can limit the columns for Users with a finder but not for the ‘throughs’ tables (GroupsMembers and Grades). Any ideas? is it possible?

> //GroupsController code
> 
> $mdlGroup = $this->MdlGroups->get($id, [
>             'contain' => ['MdlCourse', 'MdlUser' => ['finder' => 'limitRows'], 'MdlUser.MdlGradeItems'],
>             'finder' => 'limitRows',
>         ]);
> 
> //GroupsTable code
> $this->belongsToMany('MdlUser', [
>             'joinTable' => 'MdlUser',
>             'through' => 'MdlGroupsMembers',
>             'foreignKey' => 'groupid',
>             'targetForeignKey' => 'userid',
>         ]);
> 
> //GroupsMembers code 
> $this->belongsTo('MdlUser', [
>             'foreignKey' => 'userid',
>             'joinType' => 'INNER',
>         ]);
>         $this->belongsTo('MdlGroups', [
>             'foreignKey' => 'groupid',
>             'joinType' => 'INNER'
>         ]);
> 
> //UserTable code
> $this->belongsToMany('MdlGroups', [
>             'joinTable' => 'MdlGroups',
>             'through' => 'MdlGroupsMembers',
>             'foreignKey' => 'userid',
>             'targetForeignKey' => 'groupid',
>         ]);
>         $this->belongsToMany('MdlGradeItems', [
>             'joinTable' => 'MdlGradeItems',
>             'through' => 'MdlGradeGrades',
>             'foreignKey' => 'userid',
>             'targetForeignKey' => 'itemid',
>         ]);