Exports this model to a file.

        @param filepath: File to be exported to.
        @type filepath: str

def export_to_file(self, filepath, level_prefix = '  '):
        """
        Exports this model to a file.

        @param filepath: File to be exported to.
        @type filepath: str
        """
        xmldom = self.export_to_dom()
        xmlstr = xmldom.toprettyxml(level_prefix, '\n',)


        f = open(filepath, 'w')
        f.write(xmlstr)
        f.close()