Can a defendant appeal from a judgment of conviction upon a guilty plea?

^4. Section 1237.5 limits appeals from judgments following guilty pleas as follows: "No appeal shall be taken by the defendant from a judgment of conviction upon a plea of guilty" except where the defendant has filed a written statement in the trial court "showing reasonable constitutional, jurisdictional, or other grounds going to the legality of the proceedings" (id., subd. (a)), and the court has executed and filed a certificate of probable cause for such an appeal (id., subd. (b)). (See People v. DeVaughn (1977) 18 Cal.3d 889, 895 (DeVaughn).)