fixup! Fix ORM class inheritance hierarchy

bw2data/project.py

@@ -7,7 +7,7 @@
 from copy import copy
 from functools import partial
 from pathlib import Path
-from typing import Any, Optional, Sequence, TypeVar
+from typing import TYPE_CHECKING, Any, Optional, Sequence
 
 import wrapt
 from bw_processing import safe_filename
@@ -23,6 +23,10 @@
 from bw2data.utils import maybe_path
 
 
+if TYPE_CHECKING:
+    from bw2data import revisions
+
+
 READ_ONLY_PROJECT = """
 ***Read only project***