ENH: added populating order of entities from bids schema copy

heudiconv/bids/schema.py

@@ -0,0 +1,30 @@
+from pathlib import Path
+import yaml
+
+
+def _load_entities_order():
+    # we carry the copy of the schema
+    schema_p = Path(__file__).parent / "data" / "schema"
+    with (schema_p / "objects" / "entities.yaml").open() as f:
+        entities = yaml.load(f)
+
+    with (schema_p / "rules" / "entities.yaml").open() as f:
+        entities_full_order = yaml.load(f)
+
+    # map from full name to short "entity"
+    return [entities[e]["entity"] for e in entities_full_order]
+
+
+class BIDSFile:
+    """ as defined in https://bids-specification.readthedocs.io/en/stable/99-appendices/04-entity-table.html
+    which might soon become machine readable
+    order matters
+    """
+
+    _known_entities = _load_entities_order()
+
+
+# TEMP: just for now, could be moved/removed
+def test_BIDSFile():
+    assert BIDSFile._known_entities[:2] == ['sub', 'ses']
+    print(BIDSFile._known_entities)