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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_connectivity_topos(self, fig=None):
 """ Plot scalp projections of the sources. This function only plots the topos. Use in combination with connectivity plotting. Parameters fig : {None, Figure object}, optional Where to plot the topos. f set to **None**, a new figure is created. Otherwise plot into the provided figure object. Returns ------- fig : Figure object Instance of the figure in which was plotted. """

        self._prepare_plots(True, False)
        if self.plot_outside_topo:
            fig = self.plotting.plot_connectivity_topos('outside', self.topo_, self.mixmaps_, fig)
        elif self.plot_diagonal == 'topo':
            fig = self.plotting.plot_connectivity_topos('diagonal', self.topo_, self.mixmaps_, fig)
        return fig