def _bregman_map(M, lambda_k, diff_d_k):
    """ Bregman map, according to [1], Eq. 2.9, with f(x) := -d(lambda), and M*psi(x,y) := M/2*||lambda-lambda_k||_2
    Old:
    lambda_bregman = lambda_k + float(1.0)/M*diff_d_k
    return self._project_on_dual_feasible_set(lambda_bregman)
    """
    return lambda_k + float(1.0) / M * diff_d_k
