sestate: re-implement is_feasible

        Solve the PC and return True if it is sat. Handy in the cases

        when the state is constructed manually.

        """

        return self.is_sat(*self.constraints())

        C = self.constraints()

        if not C:

            return True

        r = self._solver.try_is_sat(1000, *C)

        if r is not None:

            return r

        em = self.expr_manager()

        r = try_solve_incrementally([], C, em)

        if r is not None:

            return r

        return self._solver.is_sat(em.conjunction(*C))

    def concretize(self, *e):

        return self._solver.concretize(self.constraints(), *e)