Ubergraph descendants() treats bare string CURIE input as characters

Tested with oaklib==0.7.0rc7 and Python 3.12.

UbergraphImplementation.descendants() appears to advertise support for Union[str, List[str]] input, but a bare string CURIE is treated as an iterable of characters. Passing the same CURIE inside a list works.

Reproducer

from oaklib import get_adapter
import importlib.metadata as md

print(md.version("oaklib"))  # 0.7.0rc7
adapter = get_adapter("ubergraph:")

print(list(adapter.descendants(
    "GO:0008150",
    predicates=["rdfs:subClassOf"],
    reflexive=False,
))[:5])
# []
# plus warnings such as:
# WARNING:root:Not a curie: G
# WARNING:root:Not a curie: O
# WARNING:root:Not a curie: 0

print(list(adapter.descendants(
    ["GO:0008150"],
    predicates=["rdfs:subClassOf"],
    reflexive=False,
))[:5])
# ['GO:0007269', 'GO:0007283', 'GO:0007286', 'GO:0007288', 'GO:0007289']

Expected behavior

Either:

• bare string CURIE input should behave the same as a one-element list, matching the apparent Union[str, List[str]] contract, or
• the method signature/docs should require a list and reject a bare string clearly.

Current downstream workaround

In linkml-term-validator, I had to wrap all graph traversal start CURIEs in a list before calling ancestors() or descendants() so Ubergraph does not iterate over the characters in a CURIE string.

Start at UbergraphImplementation.descendants() and compare its behavior for a bare CURIE string with a one-element list; also check the related ancestors() entry point. Re-run the Python reproducer against the Ubergraph adapter and confirm that string input no longer produces character-by-character CURIE warnings and matches list input.