private boolean hasInputTrait(Model model, MemberShape member) {
        return model.getShape(member.getContainer()).filter(shape -> shape.hasTrait(InputTrait.ID)).isPresent();
    }
Validates that only backward compatible changes are made to
structure member nullability to ensure that if something was
previously nullable to clients then it continue to be nullable
and vice versa.
smithy-diff/src/main/java/software/amazon/smithy/diff/evaluators/ChangedNullability.java