plot two band structure for comparison. One is in red the other in blue.
        The two band structures need to be defined on the same symmetry lines!
        and the distance between symmetry lines is
        the one of the band structure used to build the PhononBSPlotter

        Args:
            another PhononBSPlotter object defined along the same symmetry lines

        Returns:
            a matplotlib object with both band structures

def plot_compare(self, other_plotter):
        """
        plot two band structure for comparison. One is in red the other in blue.
        The two band structures need to be defined on the same symmetry lines!
        and the distance between symmetry lines is
        the one of the band structure used to build the PhononBSPlotter

        Args:
            another PhononBSPlotter object defined along the same symmetry lines

        Returns:
            a matplotlib object with both band structures

        """

        data_orig = self.bs_plot_data()
        data = other_plotter.bs_plot_data()

        if len(data_orig['distances']) != len(data['distances']):
            raise ValueError('The two objects are not compatible.')

        plt = self.get_plot()
        band_linewidth = 1
        for i in range(other_plotter._nb_bands):
            for d in range(len(data_orig['distances'])):
                plt.plot(data_orig['distances'][d],
                         [e[i] for e in data['frequency']][d],
                         'r-', linewidth=band_linewidth)

        return plt