Injecting JSON-LD context when parsing

[Natureshadow]

When parsing a JSON-LD document, RDFlib will analyze its context and load all URI contexts from their remotes.

As a best practice and to improve performance, it is a good idea to cache such contexts (which, as I see it, RDFlib doesn't do), or even inject expected contexts before loading.

A major part of this was already discussed in #1844 from a security point of view, but that's not the background here. (I have a particularly bad example where the JSON-LD representation of the context has vanished from its URI.)

In other words: I am about to load a document, and I know that it will contain https://example.com/ns/foo# as context. My application knows this context, and I want to prevent RDFlib from laoding it remotely, and instead provide it with the known context. I am not so much concerned about security here (if the context were dereferencable, that would be great), I just want to spare the parser the effort of loading it.

Has anybody doen that already, or has a nice idea of how to do it?