In a chapter 9 case, the court fixes the time within which proofs of claim or interest may be filed. Fed. R. Bankr. P. 3003(c)(3). Many creditors may not be required to file a proof of claim in a chapter 9 case. For example, a proof of claim is deemed filed if it appears on the list of creditors filed by the debtor, unless the debt is listed as disputed, contingent, or unliquidated. 11 U.S.C. § 925. Thus, a creditor must file a proof of claim if the creditor's claim appears on the list of creditors as disputed, contingent, or unliquidated.