def feasible_ratio(self, solutions):
        """counts for each coordinate the number of feasible values in
        ``solutions`` and returns an array of length ``len(solutions[0])``
        with the ratios.

        `solutions` is a list or array of repaired ``Solution``
        instances,

        """
        raise NotImplementedError('Solution class disappeared')
        count = np.zeros(len(solutions[0]))
        for x in solutions:
            count += x.unrepaired == x
        return count / float(len(solutions))
counts for each coordinate the number of feasible values in
        ``solutions`` and returns an array of length ``len(solutions[0])``
        with the ratios.

        `solutions` is a list or array of repaired ``Solution``
        instances,