Plot the PAW projectors.

        Args:
            ax: matplotlib :class:`Axes` or None if a new figure should be created.

        Returns: `matplotlib` figure

def plot_projectors(self, ax=None, fontsize=12, **kwargs):
        """
        Plot the PAW projectors.

        Args:
            ax: matplotlib :class:`Axes` or None if a new figure should be created.

        Returns: `matplotlib` figure
        """
        ax, fig, plt = get_ax_fig_plt(ax)
        title = kwargs.pop("title", "Projectors")
        ax.grid(True)
        ax.set_xlabel('r [Bohr]')
        ax.set_ylabel(r"$r\tilde p\, [Bohr]^{-\frac{1}{2}}$")

        #ax.axvline(x=self.paw_radius, linewidth=2, color='k', linestyle="--")
        #ax.annotate("$r_c$", xy=(self.paw_radius + 0.1, 0.1))

        for state, rfunc in self.projector_functions.items():
            ax.plot(rfunc.mesh, rfunc.mesh * rfunc.values, label="TPROJ: " + state)

        ax.legend(loc="best", shadow=True, fontsize=fontsize)

        return fig