Exposing Workflow._graph.nodes_iter() through the public API

[ischwabacher]

Maybe I'm doing this the wrong way, but I have a hierarchical workflow that needs to connect some boilerplate fields (dimension and terminal_output, in this case) from the input node to all of the nodes in the workflow that expect these inputs. I could obtain the list of nodes to iterate over with map(workflow.get_node, workflow.list_node_names()), but because this flattens the graph, it would only be possible at the top level and would prevent me from using the same trick on my sub-workflows (because the inputs would collide). The list of nodes that I actually want to connect to is precisely workflow._graph.nodes(), and philosophically I would like the ability to consider sub-workflows as black boxes, which I currently can't figure out how to do using the public API.

I understand not wanting to expose Workflow._graph directly, but is there a reason not to expose an iterator over the graph's nodes?

[ischwabacher]

After playing with this some more, it looks like the reason for this is that sub-workflows aren't black boxes. Closing in favor of #819.