Missing "openclass" WidgetMetaClass parameter in old Orange3 versions
Introduced here: https://github.com/biolab/orange-widget-base/commit/86f4a5d71061fe29f28c4df92acc5e5c661404bc
First released in orange-widget-base 4.0.1 so that's Orange 3.23.0 (tomwer seems to be on 3.20.1)
Edited by Wout De Nolf