In Graham v. State, 119 Md. App. 444, 705 A.2d 82 (1998), an automobile passenger, following a valid traffic stop of the automobile for speeding, was detained for a period of 25 minutes while a K-9 unit responded to the scene. Judge Davis's opinion pointed out that the purpose of the traffic stop had long since been fully effectuated. At the point in time when Davis was arrested, the purpose of the traffic stop had been effectuated. In other words, approximately five minutes, more or less, after the initial stop, Trooper Kissner had concluded his official duties with respect to the traffic stop ....119 Md. App. at 468. A traffic stop must not be prolonged to facilitate the arrival of a K-9 unit. In the case presently before us, the prolongation of a detention because the K-9 unit is detained elsewhere must be viewed as contrary to the diligence required under a Fourth Amendment reasonableness analysis. Id.