Underscore similar to fn.py _

Creating to discuss possibly implementing and better integrating something similar to _ in fn.py. From the 0.5.0 milestones:

Another idea is to implement the _ operator from fn.py. It is quite useful, but its overkill to require the library as a dependency and gimmicky to check if it exists just to import. This might open doors to integrate it more deeply as well.

[EntilZha]

With progress on a parallel computation engine, one possible reason for wanting this is that fn._ does not serialize well. Creating a custom one the specifically is meant for this could fix that problem

[EntilZha]

Closing for now, will re-open if it seems like it will be worked on soon.