code: def add_node_collection(self, node, collection):
          
          assert node in self.node2pending
          if self.collection_is_completed:
              # A new node has been added later, perhaps an original one died.
              # .schedule() should have
              # been called by now
              assert self.collection
              if collection != self.collection:
                  other_node = next(iter(self.node2collection.keys()))
                  msg = report_collection_diff(
                      self.collection, collection, other_node.gateway.id, node.gateway.id
                  )
                  self.log(msg)
                  return
          self.node2collection[node] = list(collection)
docs: Add the collected test items from a node
  
          The collection is stored in the ``.node2collection`` map.
          Called by the ``DSession.worker_collectionfinish`` hook.