Except as provided in sections 43-254.01 and 43-277.01 and unless sooner released, a juvenile taken into custody or remaining in custody under sections 43-248, 43-250, 43-253, and 43-254 shall be brought before the juvenile court for an adjudication hearing as soon as possible but, in all cases, within a six-month period after a petition is filed. If the juvenile is not brought before the juvenile court within such period of time, he or she shall be released from custody, except that such hearing shall not be had until there is before the court the juvenile when charged under subdivision (1), (2), (3)(b), or (4) of section 43-247, and in all cases the juvenile’s custodian or person with whom he or she may be, or his or her parent or guardian, or, if they fail to appear, and in all cases under subdivision (3)(a) of section 43-247, a guardian ad litem. The computation of the six-month period provided for in this section shall be made as provided in section 29-1207, as applicable.