functionality to sum or subtract cols in schema

[AnneONS]

Pull Request submission

To create the PNP output file for the national accounts, it's necessary to map the questions we use in the survey
to the "old" questions they use in national accounts.

Previously this was done in the script directly, but in this code new lines are added to the schema to indicate which columns should be added to or subtracted from the column in question.

Closes or fixes

• Detail the ticket(s) you are closing with this PR
  Closes #

Code

• Code runs The code runs on my machine and/or CDSW
• Conflicts resolved There are no conflicts (I have performed a rebase if necessary)
• Requirements My/our code functions according to the requirements of the ticket
• Dependencies I have updated the environment yaml so it includes any new libraries I have used
• Configuration file updated any high level parameters that the user may interact with have been put into the config file (and imported to the script)
• Clean Code
  • Code is as PEP 8 compliant as I can humanly make it
  • Code passess flake8 linting check
  • Code adheres to DRY
• Type hints All new functions have type hints

Documentation

Any new code includes all the following forms of documentation:

• Function Documentation Docstrings within the function(s')/methods have been created
  • Includes Args and returns for all major functions
  • The docstring details data types
• Updated Documentation: User and/or developer working doc has been updated

Data

• All data needed to run this script is available in Dev/Test
• All data is excluded from this pull request
• Secrets checker pre-commit passes

Testing

• Unit tests Unit tests have been created and are passing or a new ticket to create tests has been created

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Peer Review Section

• All requirements install from (updated) requirements.txt
• Documentation has been created and is clear - check the working document
• Doctrings (Google format) have been created and accurately describe the function's functionality
• Unit tests pass, or if not present a new ticket to create tests has been created
• Code runs The code runs on reviewer's machine and/or CDSW

Final approval (post-review)

The author has responded to my review and made changes to my satisfaction.

• I recommend merging this request.

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Review comments

Insert detailed comments here!

These might include, but not exclusively:

• bugs that need fixing (does it work as expected? and does it work with other code
  that it is likely to interact with?)
• alternative methods (could it be written more efficiently or with more clarity?)
• documentation improvements (does the documentation reflect how the code actually works?)
• additional tests that should be implemented (do the tests effectively assure that it
  works correctly?)
• code style improvements (could the code be written more clearly?)
• Do the changes represent a change in functionality so the version number should increase? Start a discussion if so.
• As a review you can generates the same outputs from running the code

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Be critical and clear, but not mean. Ask questions and set actions.

[AnneONS]

for @abaizan

[abaizan]

In this review I have:

• run main.py locally (no errors)
• reviewed sum_subtract_cols and the tests for it
• only addition was a small clarification in the docstrings