Is a certificate of probable cause necessary to challenge the exercise of individualized sentencing within an agreed maximum sentence?

"[A] certificate of probable cause is not required to challenge the exercise of individualized sentencing discretion within an agreed maximum sentence. Such an agreement, by its nature, contemplates that the court will choose from among a range of permissible sentences within the maximum, and that abuses of this discretionary sentencing authority will be reviewable on appeal, as they would otherwise be. Accordingly, such appellate claims do not constitute an attack on the validity of the plea, for which a certificate is necessary." ( People v. Buttram, supra , 30 Cal.4th at pp. 790791, 134 Cal.Rptr.2d 571, 69 P.3d 420 ; see id. at p. 777, 134 Cal.Rptr.2d 571, 69 P.3d 420 ["Unless it specifies otherwise, a plea agreement providing for a maximum sentence inherently reserves the parties right to a sentencing proceeding in which (1) ... they may litigate the appropriate individualized sentence choice within the constraints of the bargain and the court's lawful discretion, and (2) appellate challenges otherwise available against the court's exercise of that discretion are retained"].)