Does section 1237.5 apply to a challenge of a sentence imposed after a plea of guilty or no contest?

" 'In determining whether section 1237.5 applies to a challenge of a sentence imposed after a plea of guilty or no contest, courts must look to the substance of the appeal: "the crucial issue is what the defendant is challenging, not the time or manner in which the challenge is made." [Citation.] Hence, the critical inquiry is whether a challenge to the sentence is in substance a challenge to the validity of the plea, thus rendering the appeal subject to the requirements of section 1237.5.' " (People v. Buttram (2003) 30 Cal.4th 773, 781-782.)