Add documentation and type hints for rdflib.query.Result and rdflib.graph.Graph

[edmondchuc]

Add documentation and type hints for rdflib.query.Result. Update documentation and type hints for rdflib.graph.Graph.

I am keen to work on adding documentation and type hints to rdflib. rdflib.query.Result's serialize() is an example of this work.
Please leave any comments on styling and conventions.

Proposed Changes

• Progressively update documentation and add type hints everywhere
• Remove sphinx-style documentation such as parameter and return types and update with newer Python type hints.

For the second point, an example would be to remove

rdflib/rdflib/graph.py

Line 1150 in c5ff127

:returntype: rdflib.query.QueryResult

and replace it with using python type hints.

E.g.

def query(
        self,
        ...
        **kwargs
    ) -> query.Result:

Sphinx also understands this and adds hyperlinks automatically as well.

If this is acceptable, we should draft a guideline on adding/updating documentation and type hints to the rdflib codebase.

[coveralls]

Coverage decreased (-0.04%) to 75.435% when pulling 2077524 on edmondchuc:feat/sparql-result-serializer-docs into c5ff127 on RDFLib:master.

[FlorianLudwig]

Thanks for improving the docs, that is really welcome 👍

My opinion: the :returntype: in the doc string can be removed if there is a type declaration but parameter descriptions, like :param destination: Path of file output. cannot.