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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 on_click_plot_widget(self, event):
 """ When the plot control is toggled, set visibility and hand down source"""

        self.plot.source = self.sources
        self.plot.visible = event.new
        if self.plot.visible:
            self.plot.watchers.append(
                self.select.widget.link(self.plot, value='source'))