API Deprecate paired_distances and paired_*_distances

[Micky774]

Background

We have several public functions paired_*_distances which exist primarily as specialized implementations for the public paired_distances function. This function is thus either a wrapper around the specialized paired_*_distances or a simple iteration over the input data. During the drafting meeting, we discussed the deprecation of these functions. This discussion continued on a recent PR (start here). I wanted to open this to see if we could come to a quick consensus on our intent for the paired_* functions.

Personally, I definitely want to see paired_*_distances deprecated. I have no idea how widely used paired_distances is in practice. I believe @thomasjpfan has a better sense of this after some github searches. If it is not too widely used, I am also in favor of deprecating it as a whole.

As @adrinjalali mentioned (cf. comment) the paired_distances function is a really light function that most users ought to be able to write themselves. It doesn't really make sense for us to provide it for them...

cc: @scikit-learn/core-devs

Edit: Consensus is to deprecate both paired_*_distances and paired_distances

[jjerphan]

I am +1 regarding deprecating and removing paired_*_distances.

I think we need to know if paired_distances is significantly used before taking any decision (I do not know any alternative to the global search of GitHub).

[adrinjalali]

I'm in favor of deprecating them all, if too many users complain, we can reverse action, but the implementation is trivial, so we shouldn't have any issues removing them.

[Micky774]

@StefanieSenger this is a medium-scope task, in case you would be interested in taking it on. If not I can mark it as help wanted 😄

[Shreesha3112]

Would like to open PR

[StefanieSenger]

Seen the ping only now. If there is something I can support you with, @Shreesha3112, please let me know. :)