United States v. Myers, 804 F.3d 1246 (9th Cir. Sept. 14, 2015), amended Oct. 28, 2015 (affirming federal conviction, in which the defendant and government reached a plea deal during a settlement conference conducted by a magistrate judge, even though United States v. Davila, 133 S. Ct. 2139 (2013) makes clear that Fed. R. Crim. P. 11(c)(1) imposes a categorical bar on judicial participation in plea negotiations, even when the judicial participation is both requested by the defendant and sanctioned by the district court's local rules, Rule 11(c)(1) is waivable by the defendant, because the defendant failed to establish the alleged error affected his substantial rights because the record is bereft of evidence indicating that he suffered from any prejudice due to the magistrate judge's participation in the settlement conference).