er has no power to compel the custodian of the material to risk a contempt citation for his refusal to comply" (internal quotation marks omitted)); Overby v. United States Fid. & Guar. Co., 224 F.2d 158, 162 & n.5 (5th Cir. 1955) (exercising interlocutory jurisdiction and citing Perlman in a civil action to recover damages