Every person unlawfully imprisoned or restrained of his liberty, under any pretense whatever, may prosecute a writ of habeas corpus, to inquire into the cause of such imprisonment or restraint. NOTE: Section 135.10 is identical to former § 1473. See also Cal. Pen. Code § 1473 (same). See generally B. Witkin, California Criminal Procedure Habeas Corpus and Other Extraordinary Writs §§ 788-832 (1963, Supp. 1973).