Added details to docs for accessing variables on nodes and subgraphs

[dlcole3]

I have gotten some feedback from some different people that the graphs are not always intuitive to someone with little optimization background, and when I was first using Plasmo, I did not understand how to acccess solutions or variables. I added to the gas network tutorial a section on querying solutions and accessing variables and explain the "nested" reference structure of nodes on subgraphs and variables on nodes.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.96%. Comparing base (1702300) to head (ff4f2b5).

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #102      +/-   ##
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+ Coverage   87.79%   87.96%   +0.16%     
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  Files          19       19              
  Lines        2368     2368              
==========================================
+ Hits         2079     2083       +4     
+ Misses        289      285       -4     

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[jalving]

Thanks @dlcole3, better documentation is always welcome. You hit on some interesting points about how confusing this example can be with regard to ordering of subgraphs. Once the next release is done (it's getting close) we will revisit a lot of documentation updates and improved tutorials.

[dlcole3]

Thanks @dlcole3, better documentation is always welcome. You hit on some interesting points about how confusing this example can be with regard to ordering of subgraphs. Once the next release is done (it's getting close) we will revisit a lot of documentation updates and improved tutorials.

No problem @jalving. I would also like to add some details on the aggregation mapping, but I have not gotten to that yet. I had another grad student reach out to me about using the gas network model for a project they are working on, so I figured I would put this information in the docs so that I could point them to it.