Function unresolved_contexts 

pub fn unresolved_contexts(
    registry: &Registry,
    document: &Value,
    limits: Limits,
) -> Result<Vec<String>, Error>

Every context document names, directly or through a context it names, that registry does not hold: what a caller that fetches contexts has to fetch before canonize can succeed.

Each one missing is read as ActivityStreams for the rest of the pass, as crate::expand reads it, so that one pass finds every one the document names itself; a context one of those names in turn is found once that one has been added. Empty when nothing is missing.

Errors

When the document cannot be expanded for some reason other than a missing context. An error met after a context was found missing is not reported, since the missing context may be its cause; the missing ones are.