def _write_bin(self, stream, byte_order):
        '''
        Save a PLY element to a binary PLY file.  The element may
        contain list properties.

        '''
        for rec in self.data:
            for prop in self.properties:
                prop._write_bin(rec[prop.name], stream, byte_order)
Save a PLY element to a binary PLY file.  The element may
        contain list properties.