Improve the "replaced by" and "consider" term extraction (#209)

* Extract the text, even if there are no attributes on that tag
* Add warning on missing datatype in `replaced_by` and `consider` RDF/XML parsing

---------

Co-authored-by: Martin Larralde <martin.larralde@embl.de>

pronto/parsers/rdfxml.py

@@ -419,7 +419,13 @@ def _extract_term(self, elem: etree.Element, curies: Dict[str, str]):
  iri = attrib[_NS["rdf"]["resource"]]
  curie = curies.get(iri) or self._compact_id(iri)
  termdata.replaced_by.add(curie)
- elif _NS["rdf"]["datatype"] in attrib:
+ elif text is not None:
+ if _NS["rdf"]["datatype"] not in attrib:
+ warnings.warn(
+ "no datatype in `IAO:0100001` annotation",
+ SyntaxWarning,
+ stacklevel=2,
+ )
  curie = curies.get(text) or self._compact_id(text)
  termdata.replaced_by.add(curie)
  else:
@@ -433,7 +439,13 @@ def _extract_term(self, elem: etree.Element, curies: Dict[str, str]):
  iri = attrib[_NS["rdf"]["resource"]]
  curie = curies.get(iri) or self._compact_id(iri)
  termdata.consider.add(curie)
- elif _NS["rdf"]["datatype"] in attrib:
+ elif text is not None:
+ if _NS["rdf"]["datatype"] not in attrib:
+ warnings.warn(
+ "no datatype in `oboInOwl:consider` annotation",
+ SyntaxWarning,
+ stacklevel=2,
+ )
  curie = curies.get(text) or self._compact_id(text)
  termdata.consider.add(curie)
  else: