def summary_str(self) -> str:
        """Return a string that summarizes the graph."""
        return '{}\n'.format(self) + '\n'.join(
            '{}: {}'.format(label, value)
            for label, value in self._describe_list()
        )
def summary_str ( self ) -> str : return '{}\n' . format ( self ) + '\n' . join ( '{}: {}' . format ( label , value ) for label , value in self . _describe_list ( ) )
Return a string that summarizes the graph.