get the higher item in a product structure based on several ItemTypes

Many thanks for your help Yoann! That's it, I read the documentation for weeks but cannot firgure out the use of newItem. Intuitively, when I read this code, I see you creating an item of type MyRelationship then setting the related_id to the value contained in MyItemId. But, tell me if I understand it well, what you do is to look for relationships of type MyRelationship whose related_id is MyItemId? So the relationship I am looking for will be contained in Rel?