Graph as Merkel tree ish thing

[CJ-Wright]

The idea would be to have the nodes have a representation of themselves which reference their characteristic variables (their name, the name/module of any incoming functions, args, kwargs, etc.) plus their order in the execution and their parent. All of this will be hashed. Thus to check if a graph is different from another we can check if any of the nodes has a different characteristic hash.

Note that these hashes may not be unique, since source nodes would all look the same, but that may be ok. As a consequence we won't be able to use these as node names for networkx.

[CJ-Wright]

It is important to note that this would go a long way to checking if two pipelines are the same.

[CJ-Wright]

(t/h to @tacaswell )

[CJ-Wright]

Done in SHED