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See https://peps.python.org/pep-0758/ for more details. We implement this by extending the syntax for exceptions and exception groups so that the `type` field can now contain either an expression (which matches the old behaviour), or a comma-separated list of at least two elements (representing the new behaviour). We model the latter case using a new node type `exception_list`, which in `tsg-python` is simply mapped to a tuple. This means it matches the existing behaviour (when the tuple is surrounded by parentheses) exactly, hence we don't need to change any other code. As a consequence of this, however, we cannot directly parse the Python 2.7 syntax `except Foo, e: ...` as `except Foo as e: ...`, as this would introduce an ambiguity in the grammar. Thus, we have removed support for the (deprecated) 2.7-style syntax, and only allow `as` to indicate binding of the exception. The syntax `except Foo, e: ...` continues to be parsed (in particular, it's not suddenly a syntax error), but it will be parsed as if it were `except (Foo, e): ...`, which may not give the correct results. In principle we could extend the QL libraries to account for this case (specifically when analysing Python 2 code). In practice, however, I expect this to have a minor impact on results, and not worth the additional investment at this time.