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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 compute_qpi(self):
 """Compute model data with current parameters Returns ------- qpi: qpimage.QPImage Modeled phase data Notes ----- The model image might deviate from the fitted image because of interpolation during the fitting process. """

        kwargs = self.model_kwargs.copy()
        kwargs["radius"] = self.radius
        kwargs["sphere_index"] = self.sphere_index
        kwargs["center"] = [self.posx_offset, self.posy_offset]
        qpi = self.sphere_method(**kwargs)
        # apply phase offset
        bg_data = np.ones(qpi.shape) * -self.pha_offset
        qpi.set_bg_data(bg_data=bg_data, which_data="phase")
        return qpi