Develop causality

[vdeltatto]

I re-defined the argument k for the methods of the class MetricComparisons as the order of the farthest neighbour considered, instead of computing the imbalance using only the neighbour of order k. I also added two new methods return_inf_imb_causality and return_inf_imb_causality_target_rank in the MetricComparisons class in order to compute the Imbalance of the causal test (weight*X(t), Y(t)) -> Y(t+tau). Since in this case it is difficult to use a single data set as input of the constructor of MetricComparisons, the data sets X(t), Y(t) and Y(t+tau) are given in input directly to the these additional methods. If you think that it is worth to create a new class for the causality methods, I can do it and give these data sets as input of the class constructor.

In the test folder I added a new npy file to test the functions (in test_information_imbalance.py)

[codecov-commenter]

Codecov Report

Patch coverage: 60.00% and project coverage change: -0.31 :warning:

Comparison is base (c93d472) 81.40% compared to head (4386d27) 81.10%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #90 +/- ## ========================================== - Coverage 81.40% 81.10% -0.31% ========================================== Files 10 10 Lines 1506 1519 +13 ========================================== + Hits 1226 1232 +6 - Misses 280 287 +7 ``` | [Impacted Files](https://app.codecov.io/gh/sissa-data-science/DADApy/pull/90?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [dadapy/metric\_comparisons.py](https://app.codecov.io/gh/sissa-data-science/DADApy/pull/90?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-ZGFkYXB5L21ldHJpY19jb21wYXJpc29ucy5weQ==) | `67.83% <45.45%> (-1.31%)` | :arrow_down: | | [dadapy/\_utils/metric\_comparisons.py](https://app.codecov.io/gh/sissa-data-science/DADApy/pull/90?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-ZGFkYXB5L191dGlscy9tZXRyaWNfY29tcGFyaXNvbnMucHk=) | `90.90% <77.77%> (-4.10%)` | :arrow_down: |

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[AldoGl]

Hi @vdeltatto, great work! This is indeed a very valuable addition to the package.

Flak8 highlights the following errors

• dadapy/metric_comparisons.py:616:69: B006 Do not use mutable data structures for argument defaults. They are created during function definition time. All calls to the function reuse this one instance of that data structure, persisting changes between them.
• dadapy/metric_comparisons.py:618:1: D202 No blank lines allowed after function docstring
• dadapy/metric_comparisons.py:618:1: D400 First line should end with a period
• dadapy/metric_comparisons.py:647:1: D400 First line should end with a period

I will suggest some specific code changes to take care of them