Writes a title header in the document body,
           with an optional depth level

def write_title(self, title, level=1, id=None):
        """Writes a title header in the document body,
           with an optional depth level
        """
        if id:
            self.write('<h{lv} id="{id}">{title}</h{lv}>',
                       title=title, lv=level, id=id)
        else:
            self.write('<h{lv}>{title}</h{lv}>',
                       title=title, lv=level)