I must admit I don’t even understand the docs 
my example above works perfectly fine,
for example, if I create the parent beforehand and add a uid field to the parent with the uid of the node I can achieve what I want.
In general, I was wondering if there is a way to avoid that initial creation of the parent node because its much more effort to inject an uid field in the json array at every parent object.
I was wondering if it might be possible to set a constraint on the containerId which would lead dgraph to automatically resolve the fact that there should be only one node with that exact containerID