[Maya-Python] MItDependencyGraph and render layer adjustments

[Henry Foster]

I've run into a particularly weird problem I'm not sure how to solve.

I need to traverse shading networks in order to get all upstream nodes. I'm
trying to use the Python API to do this, via the MItDependencyGraph
iterator. This is great and fast, except in the weird case where a
connection exists on some render layers, but NOT on the defaultRenderLayer.
Even if I switch to that layer and I can see all the connections in the
Hypershade, if the connection doesn't exist on the defaultRenderLayer, the
iterator doesn't seem to be able to see it at all. The team I'm supporting
loves to use render layer overrides to have things connected on some layers
but not others, and it's not a behavior I'm in any position to change. Is
there a way to convince the iterator to traverse these connections?