Fix typing errors
Fix typing errors

Note re `_urlopen(full_link)` -> `_urlopen(Request(full_link))`

`_urlopen` expects a request object and will potentially use
`Request.full_url` which won't be available on a string.

RDFLib/rdflib,RDFLib/rdflib,RDFLib/rdflib,RDFLib/rdflib