def METHOD_NAME(p, X, Y, Z):
    """3D PSF model function with constant background - parameter vector [A, x0, y0, z0, background]"""
    A, x0, y0, z0, wxy, wz, b = p
    #return A*scipy.exp(-((X-x0)**2 + (Y - y0)**2)/(2*s**2)) + b
    #print X.shape
    return A*np.exp(-((X-x0)**2 + (Y - y0)**2)/(2*wxy**2) - ((Z-z0)**2)/(2*wz**2)) + b