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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def eval(self, x_values):
 """ Evaluate the ACE regression at any combination of independent variable values. Parameters x_values : iterable a float x-value for each independent variable, e.g. (1.5, 2.5) """

        if len(x_values) != len(self.phi_continuous):
            raise ValueError('x_values must have length equal to the number of independent variables '
                             '({0}) rather than {1}.'.format(len(self.phi_continuous),
                                                             len(x_values)))

        sum_phi = sum([phi(xi) for phi, xi in zip(self.phi_continuous, x_values)])
        return float(self.inverse_theta_continuous(sum_phi))