def print_treemap(self, format=None, output=sys.stdout, **kwargs):
        """
        Print the matrix for self's nodes.

        Args:
            format (str): output format (csv, json or text).
            output (file): file descriptor on which to write.
        """
        treemap = self.as_treemap()
        treemap.print(format=format, output=output, **kwargs)