Fixes#826. Addresses all five points the maintainer called out in
the follow-up to #825.
Source change (trustgraph-flow/trustgraph/extract/kg/ontology/extract.py):
- Added `_is_subclass_of(cls, target, ontology_subset, max_depth=100)`
helper with visited-set cycle detection + a defensive depth cap.
LLM-generated ontologies may emit cycles (A subclass_of B,
B subclass_of A); the prior while-loop would infinite-loop on that.
- Replaced both near-identical domain and range subclass walks in
`is_valid_triple` with a single call to the new helper. Net is
-20 duplicated lines + 26-line helper.
Tests (tests/unit/test_extract/test_ontology/test_prompt_and_extraction.py):
- test_is_valid_triple_subclass_is_accepted: domain expects Recipe,
actual type is Cake (subclass), validates.
- test_is_valid_triple_handles_subclass_cycle_without_infinite_loop:
A subclass_of B, B subclass_of A; call returns False within the
depth cap rather than hanging.
- test_parse_and_validate_triples_collects_entity_types_from_rdf_type:
end-to-end path: rdf:type triples build the entity_types dict,
subsequent domain-check triples validate against it.
- test_is_valid_triple_entity_types_none_default: the None default
path now has explicit coverage.
156 existing tests in tests/unit/test_extract/test_ontology still pass.
