Shows the plot using pylab.  Usually I won't do imports in methods,
        but since plotting is a fairly expensive library to load and not all
        machines have matplotlib installed, I have done it this way.

def _get_2d_plot(self, label_stable=True, label_unstable=True,
                     ordering=None, energy_colormap=None, vmin_mev=-60.0,
                     vmax_mev=60.0, show_colorbar=True,
                     process_attributes=False, plt=None):
        """
        Shows the plot using pylab.  Usually I won't do imports in methods,
        but since plotting is a fairly expensive library to load and not all
        machines have matplotlib installed, I have done it this way.
        """
        if plt is None:
            plt = pretty_plot(8, 6)
        from matplotlib.font_manager import FontProperties
        if ordering is None:
            (lines, labels, unstable) = self.pd_plot_data
        else:
            (_lines, _labels, _unstable) = self.pd_plot_data
            (lines, labels, unstable) = order_phase_diagram(
                _lines, _labels, _unstable, ordering)
        if energy_colormap is None:
            if process_attributes:
                for x, y in lines:
                    plt.plot(x, y, "k-", linewidth=3, markeredgecolor="k")
                # One should think about a clever way to have "complex"
                # attributes with complex processing options but with a clear
                # logic. At this moment, I just use the attributes to know
                # whether an entry is a new compound or an existing (from the
                #  ICSD or from the MP) one.
                for x, y in labels.keys():
                    if labels[(x, y)].attribute is None or \
                                    labels[(x, y)].attribute == "existing":
                        plt.plot(x, y, "ko", **self.plotkwargs)
                    else:
                        plt.plot(x, y, "k*", **self.plotkwargs)
            else:
                for x, y in lines:
                    plt.plot(x, y, "ko-", **self.plotkwargs)
        else:
            from matplotlib.colors import Normalize, LinearSegmentedColormap
            from matplotlib.cm import ScalarMappable
            for x, y in lines:
                plt.plot(x, y, "k-", markeredgecolor="k")
            vmin = vmin_mev / 1000.0
            vmax = vmax_mev / 1000.0
            if energy_colormap == 'default':
                mid = - vmin / (vmax - vmin)
                cmap = LinearSegmentedColormap.from_list(
                    'my_colormap', [(0.0, '#005500'), (mid, '#55FF55'),
                                    (mid, '#FFAAAA'), (1.0, '#FF0000')])
            else:
                cmap = energy_colormap
            norm = Normalize(vmin=vmin, vmax=vmax)
            _map = ScalarMappable(norm=norm, cmap=cmap)
            _energies = [self._pd.get_equilibrium_reaction_energy(entry)
                         for coord, entry in labels.items()]
            energies = [en if en < 0.0 else -0.00000001 for en in _energies]
            vals_stable = _map.to_rgba(energies)
            ii = 0
            if process_attributes:
                for x, y in labels.keys():
                    if labels[(x, y)].attribute is None or \
                                    labels[(x, y)].attribute == "existing":
                        plt.plot(x, y, "o", markerfacecolor=vals_stable[ii],
                                 markersize=12)
                    else:
                        plt.plot(x, y, "*", markerfacecolor=vals_stable[ii],
                                 markersize=18)
                    ii += 1
            else:
                for x, y in labels.keys():
                    plt.plot(x, y, "o", markerfacecolor=vals_stable[ii],
                             markersize=15)
                    ii += 1

        font = FontProperties()
        font.set_weight("bold")
        font.set_size(24)

        # Sets a nice layout depending on the type of PD. Also defines a
        # "center" for the PD, which then allows the annotations to be spread
        # out in a nice manner.
        if len(self._pd.elements) == 3:
            plt.axis("equal")
            plt.xlim((-0.1, 1.2))
            plt.ylim((-0.1, 1.0))
            plt.axis("off")
            center = (0.5, math.sqrt(3) / 6)
        else:
            all_coords = labels.keys()
            miny = min([c[1] for c in all_coords])
            ybuffer = max(abs(miny) * 0.1, 0.1)
            plt.xlim((-0.1, 1.1))
            plt.ylim((miny - ybuffer, ybuffer))
            center = (0.5, miny / 2)
            plt.xlabel("Fraction", fontsize=28, fontweight='bold')
            plt.ylabel("Formation energy (eV/fu)", fontsize=28,
                       fontweight='bold')

        for coords in sorted(labels.keys(), key=lambda x: -x[1]):
            entry = labels[coords]
            label = entry.name

            # The follow defines an offset for the annotation text emanating
            # from the center of the PD. Results in fairly nice layouts for the
            # most part.
            vec = (np.array(coords) - center)
            vec = vec / np.linalg.norm(vec) * 10 if np.linalg.norm(vec) != 0 \
                else vec
            valign = "bottom" if vec[1] > 0 else "top"
            if vec[0] < -0.01:
                halign = "right"
            elif vec[0] > 0.01:
                halign = "left"
            else:
                halign = "center"
            if label_stable:
                if process_attributes and entry.attribute == 'new':
                    plt.annotate(latexify(label), coords, xytext=vec,
                                 textcoords="offset points",
                                 horizontalalignment=halign,
                                 verticalalignment=valign,
                                 fontproperties=font,
                                 color='g')
                else:
                    plt.annotate(latexify(label), coords, xytext=vec,
                                 textcoords="offset points",
                                 horizontalalignment=halign,
                                 verticalalignment=valign,
                                 fontproperties=font)

        if self.show_unstable:
            font = FontProperties()
            font.set_size(16)
            energies_unstable = [self._pd.get_e_above_hull(entry)
                                 for entry, coord in unstable.items()]
            if energy_colormap is not None:
                energies.extend(energies_unstable)
                vals_unstable = _map.to_rgba(energies_unstable)
            ii = 0
            for entry, coords in unstable.items():
                ehull = self._pd.get_e_above_hull(entry)
                if ehull < self.show_unstable:
                    vec = (np.array(coords) - center)
                    vec = vec / np.linalg.norm(vec) * 10 \
                        if np.linalg.norm(vec) != 0 else vec
                    label = entry.name
                    if energy_colormap is None:
                        plt.plot(coords[0], coords[1], "ks", linewidth=3,
                                 markeredgecolor="k", markerfacecolor="r",
                                 markersize=8)
                    else:
                        plt.plot(coords[0], coords[1], "s", linewidth=3,
                                 markeredgecolor="k",
                                 markerfacecolor=vals_unstable[ii],
                                 markersize=8)
                    if label_unstable:
                        plt.annotate(latexify(label), coords, xytext=vec,
                                     textcoords="offset points",
                                     horizontalalignment=halign, color="b",
                                     verticalalignment=valign,
                                     fontproperties=font)
                    ii += 1
        if energy_colormap is not None and show_colorbar:
            _map.set_array(energies)
            cbar = plt.colorbar(_map)
            cbar.set_label(
                'Energy [meV/at] above hull (in red)\nInverse energy ['
                'meV/at] above hull (in green)',
                rotation=-90, ha='left', va='center')
            ticks = cbar.ax.get_yticklabels()
            # cbar.ax.set_yticklabels(['${v}$'.format(
            #     v=float(t.get_text().strip('$'))*1000.0) for t in ticks])
        f = plt.gcf()
        f.set_size_inches((8, 6))
        plt.subplots_adjust(left=0.09, right=0.98, top=0.98, bottom=0.07)
        return plt