Plots each genomic signal as a line using the corresponding
        plotting_kwargs

def signal_panel(self, ax, feature):
        """
        Plots each genomic signal as a line using the corresponding
        plotting_kwargs
        """
        for gs, kwargs in zip(self.genomic_signal_objs, self.plotting_kwargs):
            x, y = gs.local_coverage(feature, **self.local_coverage_kwargs)
            ax.plot(x, y, **kwargs)
        ax.axis('tight')
        return feature