Is a defendant's waiver of right to appeal the sentence imposed upon him?

Furthermore, defendant's waiver of his right to appeal, where, as here, he agreed to the sentence imposed, forecloses our consideration of the potential issues identified by defendant. (People v. Panizzon (1996) 13 Cal.4th 68, 76-86) A challenge to a stipulated sentence cannot be pursued on appeal without a certificate of probable cause, because the sentence term is an integral part of the plea agreement and such a challenge is actually an attack on the plea itself. (Id. at p. 79.) This is also true for the challenge to the validity of the plea based on a claim of ineffective assistance of counsel. (People v. Stubbs (1998) 61 Cal.App.4th 243, 244-245.)