def METHOD_NAME(self, inputs, outputs, partials):
    """
    Compute derivatives.
    These derivatives are correct.
    Parameters
    ----------
    inputs : Vector
        Unscaled, dimensional input variables read via inputs[key].
    outputs : Vector
        Unscaled, dimensional output variables read via outputs[key].
    partials : `Jacobian`
        Contains sub-jacobians.
    """
    x = inputs['x']
    y = outputs['y']
    partials['y', 'x'] = y ** 3 - 9.0 * y * x ** 2
    partials['y', 'y'] = 3.0 * x * y ** 2 - 3.0 * y * x ** 3