506. Whenever, in the course of an inquiry or a trial or any other proceeding under this Code before any Magistrate other than a ¹[ ²[Chief Metropolitan Magistrate or Chief Judicial Magistrate], it appears that a commission ought to be issued for the examination of a witness whose evidence is necessary for the ends of justice, and that the attendance of such witness cannot be procured without an amount of delay, expense or inconvenience which, under the circumstances of the case, would be unreasonable, ³[such Magistrate shall apply to the Chief Judicial Magistrate or the Chief Metropolitan Magistrate, to whom he is subordinate], stating the reasons for the application; ⁴[and the Chief Judicial Magistrate or the Chief Metropolitan Magistrate] may either issue a commission in the manner hereinbefore provided or reject the application.