Add kwargs style factories in Python

[karlnapf]

No description provided.

[karlnapf]

See discussion at the bottom of #4441

[karlnapf]

@sorig Check it out we now have shogun API for my_kernel = sg.kernel("GaussianKernel", log_width=1.0). One thing that would be really awesome was if the meta language examples would make use of this. Currently, it is not possible to modify say python.json in order to produce the correct output. E.g.

        "KeywordArguments": {
            "List": ", $elements",
            "Element": "$keyword = $expr",
            "Separator": ", ",
            "InitialSeperatorWhenArgs>0": false
        },

produces things like

svm = machine("LibSVM"), C1 = 1.1, kernel = k

Any change you could also have a quick hack on that?

Obviously, for the other langs, we don't want to change things (i.e. still go with the put cascades for now).

[gf712]

Maybe could add a hardcoded list of keywords to ignore?
I was thinking maybe with a comment in front of the statement in the .sg file (e.g. //ignore_kwargs:python), but that would probably make it harder to implement and probably more tedious to maintain?

[karlnapf]

I think this is a simple matter of changing the generator a bit so that it can generate the python style kwargs .... let's see what esben makes of it :)

[sorig]

A cool! I think we actually anticipated this change when doing kwargs. I documented how to do it in the original PR #4128

I think the approach documented there still works :)

[karlnapf]

Cool stuff, I should have thought that you did that :) thanks!