MouseDrop : How can I know what object is being dropped

GoJS
1

mouseDrop: function(e, node) {

        console.log("The node in mousedrop is ",node.data.key);
        console.log("The draged part  is ",part);
      }

Here is I always see the background node , How can I get the details of the node being dropped on the background node ?

2

There might be any number of nodes and links that were dropped. Look at the Diagram.selection collection.