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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 plot_rad(self, colorbar=True, cb_orientation='vertical', cb_label='$g_r$, m s$^{-2}$', ax=None, show=True, fname=None, **kwargs):
 """ Plot the radial component of the gravity field. Usage ----- x.plot_rad([tick_interval, xlabel, ylabel, ax, colorbar, cb_orientation, cb_label, show, fname, **kwargs]) Parameters tick_interval : list or tuple, optional, default = [30, 30] Intervals to use when plotting the x and y ticks. If set to None, ticks will not be plotted. xlabel : str, optional, default = 'longitude' Label for the longitude axis. ylabel : str, optional, default = 'latitude' Label for the latitude axis. ax : matplotlib axes object, optional, default = None A single matplotlib axes object where the plot will appear. colorbar : bool, optional, default = True If True, plot a colorbar. cb_orientation : str, optional, default = 'vertical' Orientation of the colorbar: either 'vertical' or 'horizontal'. cb_label : str, optional, default = '$g_r$, m s$^{-2}$' Text label for the colorbar. show : bool, optional, default = True If True, plot the image to the screen. fname : str, optional, default = None If present, and if axes is not specified, save the image to the specified file. kwargs : optional Keyword arguements that will be sent to the SHGrid.plot() and plt.imshow() methods. """

        if ax is None:
            fig, axes = self.rad.plot(colorbar=colorbar,
                                      cb_orientation=cb_orientation,
                                      cb_label=cb_label, show=False, **kwargs)
            if show:
                fig.show()

            if fname is not None:
                fig.savefig(fname)
            return fig, axes

        else:
            self.rad.plot(colorbar=colorbar, cb_orientation=cb_orientation,
                          cb_label=cb_label, ax=ax, **kwargs)