On what grounds can a motion to dismiss be dismissed on the basis that a document attached to the pleading is not contested?

attached to the [plaintiff's] pleading." Parrino v. FHP, Inc., 146 F.3d 699, 705-06 (9th Cir.1998) (alteration in original) (internal quotation marks omitted), superseded by statute on other grounds as recognized in Abrego v. Dow Chem. Co., 443 F.3d 676, 681 (9th Cir. 2006). Also, "a district court ruling on a motion to dismiss may consider a document the authenticity of which is not contested, and upon which the plaintiff's complaint necessarily relies." Id. at 706.