331 apply imputation link to target

[robertswh]

Summary

With the correct imputation link, the correct "value to impute off" and correct impute marker in place we can calculate the relevant imputed value. There are two low level functions here, one to create an imputed series, e.g. forward impute from a response, and a second to apply the relevant rows to a combined_imputation column. The higher order function runs both these function for construction, forward from result, backward from result and forward from construction.

To be able to use a generalised function for all imputation types there is an imputation config to handle the differences in implementation.

There is only one test to cover four cases in this pull request. More tests are recommended in future, however, refactoring of the function was required to get it to work for a single test case, so I just applied it to all cases.

Checklists

This pull request meets the following requirements:

• installable with all dependencies recorded
• runs without error
• follows PEP8 and project specific conventions
• appropriate use of comments, for example no descriptive comments
• functions documented using Numpy style docstings
• assumptions and decisions log considered and updated if appropriate
• unit tests have been updated to cover essential functionality for a reasonable range of inputs and conditions
• other forms of testing such as end-to-end and user-interface testing have been considered and updated as required
• tests suite passes (locally as a minimum)
• peer reviewed with review recorded

If you feel some of these conditions do not apply for this pull request, please
add a comment to explain why.

[AntonZogk]

Path("tests") / "data" / "apply_imputation_link" / "FIR_BIR_C_FIC.csv"
Not a big fan of this aproach, we combine windows path object with some strings

We can define the full path like this:
Path("tests","data","apply_imputation_link","FIR_BIR_C_FIC.csv")

[AntonZogk]

I believe this function imputes the values by creating new columns and merging them, so create and merge should go in the docstrings.

I understand this might crossover with the name of higher level function perhaps rename it to add_imputed_values?

[AntonZogk]

type hints needed

[AntonZogk]

2 verbs in function implies doing 2 things, perhaps rename to create_imputation?

[AntonZogk]

@robertswh all looking good, i have left some minor optional comments. The most important thing is that the function is nicely broken down into smaller functions and returns the right results from the complicated test scenarios ( for FI and BI imputation , construction ones not ready yet). I am happy to be merged, it's up to you about applying the comments or not.

The function has many arguments and most of them are intermediate columns generated by the low level functions, but this applies to all the low level functions so we need to consider how to pass them in a reproducible way, perhaps via a config file ? I will create a separate ticket for this.