Explain why B904 is ignored in OOP test

pyproject.toml

@@ -39,10 +39,14 @@ select = [
 
 # Per-file rule ignores
 [tool.ruff.lint.per-file-ignores]
-"binder/ipython_config.py" = ["E266"] # Trailing whitespace in comment
-"tutorial/tests/test_object_oriented_programming.py" = [
-    "B904",
-] # suppress raise ... from err
+# Trailing whitespace in comment
+"binder/ipython_config.py" = ["E266"]
+# suppress `raise ... from err`
+# Why we ignore B904 from the object-oriented tests?
+# We do want to raise an assertion error if the check on the solution function attributes fails,
+# but Python by default will raise a TypeError via vars(solution_result)
+# if the result is not a class and therefore doesn't have a __dict__ attribute.
+"tutorial/tests/test_object_oriented_programming.py" = ["B904"]
 
 # Ruff formatting
 [tool.ruff.format]