Fix HIF roundtrip test expectation

[eggpig]

Summary

This PR updates the HIF roundtrip test to assert the current HIF conversion semantics correctly.

The failing assertion expected the original HIF node id ("n1") to appear in hg.v_property[*]["name"]. That expectation does not match the implementation. In hif_to_hypergraph, v_property[*]["name"] is populated from the HIF node attribute selected by node_label, which defaults to "name". For this test fixture, the input node is:

{"node": "n1", "weight": 1.0, "attrs": {"name": "Node A"}}

So the EasyGraph vertex property name should be "Node A", while the original HIF node id "n1" is preserved separately in hg.custom_hif_nodes and in the exported HIF JSON.

Root Cause

The test mixed two different HIF concepts:

• node: the HIF node identifier, for example "n1".
• attrs.name: a user-facing node attribute, for example "Node A".

The implementation preserves both, but stores them in different places. The test was checking the HIF id in the EasyGraph attribute-name field.

Changes

• Assert that hg.v_property[*]["name"] preserves attrs.name as "Node A" / "Node B".
• Assert that the original HIF node ids "n1" / "n2" are preserved in hg.custom_hif_nodes.
• Assert that exported HIF JSON still contains the original node ids after roundtrip.
• Format the touched test file with Black/isort and remove the unused os import.

Validation

• /tmp/easygraph-ci-smoke-clean-venv/bin/python -m pytest easygraph/tests/test_hif.py -q --disable-warnings
  • 2 passed
• /tmp/easygraph-ci-smoke-clean-venv/bin/python -m pytest easygraph -q --disable-warnings
  • 813 passed, 2 skipped
• /tmp/easygraph-ci-smoke-clean-venv/bin/python -m black --check easygraph/tests/test_hif.py
• /tmp/easygraph-ci-smoke-clean-venv/bin/python -m isort --check-only easygraph/tests/test_hif.py
• git diff --check