zoom out 1 level, or to full data range

def unzoom(self, event=None, set_bounds=True):
        """ zoom out 1 level, or to full data range """
        lims = None
        if len(self.conf.zoom_lims) > 1:
            lims = self.conf.zoom_lims.pop()
        ax = self.axes
        # print 'base unzoom ', lims, set_bounds
        if lims is None: # auto scale
            self.conf.zoom_lims = [None]
            xmin, xmax, ymin, ymax = self.data_range
            ax.set_xlim((xmin, xmax), emit=True)
            ax.set_ylim((ymin, ymax), emit=True)
            if set_bounds:
                ax.update_datalim(((xmin, ymin), (xmax, ymax)))
                ax.set_xbound(ax.xaxis.get_major_locator(
                    ).view_limits(xmin, xmax))
                ax.set_ybound(ax.yaxis.get_major_locator(
                    ).view_limits(ymin, ymax))
        else:
            self.set_viewlimits()

        self.canvas.draw()