sets out the offense of filing a false bankruptcy claim. A "claim" is a document filed in a bankruptcy proceeding by a creditor of the debtor. It is sometimes also called a "proof of claim." For the purposes of this section the nature of the claim is immaterial-- i.e., the claim can be secured or unsecured, liquidated or unliquidated, disputed or undisputed. A "false" claim is one that is known by the creditor to be factually untrue at the time the claim is filed.