def transitions(self):
        """Transition matrix (sparse matrix).

        Is conjugate to the symmetrized transition matrix via::

            self.transitions = self.Z *  self.transitions_sym / self.Z

        where ``self.Z`` is the diagonal matrix storing the normalization of the
        underlying kernel matrix.

        Notes
        -----
        This has not been tested, in contrast to `transitions_sym`.
        """
        if issparse(self.Z):
            Zinv = self.Z.power(-1)
        else:
            Zinv = np.diag(1./np.diag(self.Z))
        return self.Z.dot(self.transitions_sym).dot(Zinv)