def METHOD_NAME(R, kappa_0, theta_c):
    """Convergence of the cored density profile. This routine is also for testing.
    :param R: radius (angular scale)
    :param kappa_0: convergence in the core
    :param theta_c: core radius
    :return: convergence at r
    """
    expFactor = np.exp(-((R / theta_c) ** 2))
    return kappa_0 * expFactor