To set the data, a "nodes" container must be created with at least one node ("n0") that has a `source` and `target`
The `source` is the path to the data on the page (excluding "jcr:content"). A "-" followed by a number may be used to select an index rather than a specific node. For example:
`"source": "mediaItems/images/-0/image"` will select the first child node of "images" and then return the "image" child of that node
The `source` is the path to the data on the page (excluding "jcr:content"). A "-" followed by a number may be used to select an index rather than a specific node. For example:`"source": "mediaItems/images/-0/image"` will select the first child node of "images" and then return the "image" child of that node
The `target` is the path to the node that will be set or created on the current node (the node to which bl:map is attached) to hold the returned source data
