anchor.diff:          "my_join_field": {
             "type": "join",
             "relations": {
  -            "my_parent": ["my_child", "another_child"],  <1>
  -            "another_child": "grand_child" <2>
  +            "question": ["answer", "comment"],  <1>
  +            "answer": "vote" <2>
             }
           }
         }
  
positive.code: --------------------------------------------------
  // CONSOLE
  
  <1> `my_parent` is parent of `my_child`.
  
  And multiple levels of parent/child:
  
  
negative.code:         "my_join_field": { <1>
            "type": "join",
            "relations": {
              "question": "answer" <2>
            }
          }
        }
  