The interface for getting the parent ids and link data from the current node
data. This must return an array of parent ids coupled with data (i.e. an
array of two element arrays of the form ["Parent Id", data]) for the link
between this node and the parent id.
The interface for getting the parent ids and link data from the current node data. This must return an array of parent ids coupled with data (i.e. an array of two element arrays of the form ["Parent Id", data]) for the link between this node and the parent id.
This can be modified with the Stratify#parentData method.