The __signature__ attribute was used since 2017 with success. With Python 3.10, there was an incompatibility introduced by the rlcompleter module. This was detected quite late, because there is no exception thrown in normal line completion. Using the rlcompleter module directly, the error can be seen. The problem is not the attribute itself, but PySide's need to support *multi-signature*. The signature objects are either regular compatible Signature objects, or in the multi-case, *lists* thereof. Since PyPy was implemented, the internal use of the __signature__ attribute was replaced by a get_signature() call. The attribute was never documented in the public until recently in the developer docs. We therefor can assume that removal of the attribute will cause no problems. [ChangeLog][PySide6] The non-standard __signature__ attribute of functions and classes was removed in favor of get_signature(). No Pick-to because this is meant for 6.5 Change-Id: Iaa8bb08a33db66868d949593e527b753bf989681 Fixes: PYSIDE-2101 Task-number: PYSIDE-510 Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>