def solve_nonlinear(self, params, unknowns, resids):
        """ Simple iterative solve. (Babylonian method)."""

        x = params['x']
        z = unknowns['z']
        znew = z

        iter = 0
        eps = 1.0e99
        while iter < self.maxiter and abs(eps) > self.atol:
            z = znew
            znew = 4.0 - x*z

            eps = x*znew + znew - 4.0

        unknowns['z'] = znew
        unknowns['y'] = x + 2.0*znew

        resids['z'] = eps
dataset/ETHPy150Open OpenMDAO/OpenMDAO/openmdao/test/simple_comps.py/SimpleImplicitComp.solve_nonlinear/original