Singh v. Napolitano, 619 F.3d 1101 (9th Cir. Aug. 23, 2010) (per curiam) ("In order to seek habeas relief under [28 U.S.C. 2241], as Singh does, a petitioner must first, "as a prudential matter," exhaust his or her available administrative remedies."), citing Castro-Cortez v. INS, 239 F.3d 1037, 1047 (9th Cir. 2001).