def _discover_sensitivity(self, seen: set) -> None:
        """
        Doc on parent class :meth:`HdlStatement._discover_sensitivity`
        """
        assert self._sensitivity is None, self
        ctx = self._sensitivity = SensitivityCtx()

        self._discover_sensitivity_sig(self.cond, seen, ctx)
        if ctx.contains_ev_dependency:
            return

        for stm in self.ifTrue:
            stm._discover_sensitivity(seen)
            ctx.extend(stm._sensitivity)

        # elifs
        for cond, stms in self.elIfs:
            if ctx.contains_ev_dependency:
                break

            self._discover_sensitivity_sig(cond, seen, ctx)
            if ctx.contains_ev_dependency:
                break

            for stm in stms:
                if ctx.contains_ev_dependency:
                    break

                stm._discover_sensitivity(seen)
                ctx.extend(stm._sensitivity)

        if not ctx.contains_ev_dependency and self.ifFalse:
            # else
            for stm in self.ifFalse:
                stm._discover_sensitivity(seen)
                ctx.extend(stm._sensitivity)

        else:
            assert not self.ifFalse, "can not negate event"