No, it's not possible, but that should not be a problem, as the files generated using pyuic
should never, ever be modified (the warning in those files is not to be undertaken).
Those files should always be left unmodified and only updated again with pyuic, as they are only meant to be imported in the actual program file, as explained in the official guidelines about using Designer (the "multiple inheritance approach is generally the most suggested).
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…