Sparql connector default graph

[guizsantos]

Summary of changes

This PR adds the functionality to pass the default_graph parameter from within kwargs. This will be particularly useful to the LangChain RdfGraph object usage. I am pushing a PR there that will leverage the funcionality from this PR.

Furthermore, the default_graph parameter which is passed directly to the query method has priority over the default_graph parameter set from kwargs, which should be aligned with users expected behavior and offer backwards compatibilty.

Finally, I am not sure an Issue should be created and linked or new tests should be introduced, this is actually my first ever PR on a public repository, so any guidance is appreciated.

Checklist

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.
• If the change adds new features or changes the RDFLib public API:
  • Created an issue to discuss the change and get in-principle agreement.
  • Considered adding an example in ./examples.
• If the change has a potential impact on users of this project: the changes should have no impact
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[WhiteGobo]

(I am not of the maintainers but) this looks like a good functionality.

I would catch default_graph in __init__(..., default_graph=None, ...) and save it as self.default_graph=default_graph and later default to self.default_graph instead of self.kwargs.get("default_graph"). Because currently self.kwargs is only used as params for request.

I would consider adding short docstring for SPARQLConnector.query and.update that default_graph defaults to self.kwargs["default_graph"].
A test for this functionality might be a good idea as well.

[guizsantos]

Thanks for the feedback @WhiteGobo , I have little experience with the usage of rdflib so I went for the most straightforward way to pass the parameter over. However, I agree with your thoughts there... I will update the PR accordinly.

In the matter of testing, though, I am not sure how to proceed there. Let me take a look at the current tests and try to figure it out on my own. I will report back here.

[nicholascar]

@guizsantos I'm a maintainer.

Just echoing @WhiteGobo: can you please add a short docstring? If you don't it won't be obvious at the function signature level that query() and update() can work with kwargs in addition to the function parameter option.

Oh yes: we will need a test. This is simple functionality but it's a rule of this repository that all new additions have a test. This change should be able to have a very simple test created for it that tests for 1. no default graph, default_graph and kwargs "default_graph" options.