Add function to output ParameterNode as YAML

[SylviaDu99]

WIP

fixes: #274

Added write_yaml function to output ParameterNode data to a YAML file; test_write_yaml test to produce a sample output

[codecov]

Codecov Report

Attention: Patch coverage is 91.30435% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.10%. Comparing base (cf53c6d) to head (d9a37d5).
Report is 20 commits behind head on master.

Files with missing lines	Patch %	Lines
policyengine_core/parameters/parameter_node.py	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #295      +/-   ##
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+ Coverage   79.73%   83.10%   +3.36%     
==========================================
  Files         192      193       +1     
  Lines       10057    10115      +58     
  Branches     1311     1051     -260     
==========================================
+ Hits         8019     8406     +387     
+ Misses       1753     1421     -332     
- Partials      285      288       +3     

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[anth-volk]

Thanks for your continued work on this, @SylviaDu99. This is a challenging component, so it's great to have your experience here. I made a couple of structural recommendations, but a lot boils down to these two things:

1. I'd move the meat of the function back to ParameterNode and limit the method you wrote in AtInstantLike to do just what it says - get a dictionary of attributes
2. I'd programmatically iterate over all attrs, then remove ones we don't want, instead of hard-coding what we do want, as I think the former is more maintainable.

Thanks for your work, and I look forward to chatting with you about it tomorrow.

[anth-volk]

I think the best practice here would be to keep this method as simple as possible, then do a bit more work with it where we actually use it. What I would do here is:

1. Programmatically loop over all attributes and feed into a relevant data structure
2. Return said structure

I wouldn't recurse downward here, either. I think we can do that inside our custom ParameterNode method, where we're more broadly defining what we're doing.

[anth-volk]

It's at this point where I'd do some of what you've done in AtInstantLike, though I'm not sure you need to hard-code the keys we need. I would just define a list of the keys we don't want, run the function from here, use the list to remove any keys we don't want, then recurse here, as you've done

[anth-volk]

@SylviaDu99 Thanks for your revisions to this. I decided to test this out by printing out the entirety of the -us package's parameter structure within its "gov" folder, which I'd be happy to share with you. A couple issues came up:

• The code still writes out the parent value of a relevant parameter, meaning there may be an issue in get_attr_dict's processing of the exclusion list. It also appears to add children at certain points, but I'm not certain on that, as the output file is extremely large
• I'm not 100% sure this method is 100% recursive. I think - as long as it isn't memory-intensive enough to crash - you would probably want to follow the following flow:
  • Create exclusion list in ParameterNode; perhaps don't add children here
  • Run get_attr_dict, possible even without applying the exclusion list, because we'll use children a bit lower
  • Iterate over dict and delete items contained within exclusion list
  • For child in children, write a key equivalent to the child's name value, then have the output of write_yaml tacked onto the output at that key