Pre Fallback

Key Pre Fallback in OI Term Rate refers to an optional object of type Fallback Def that is missing by default.
If supplied, the OI Term Rate is considered to be the fallback rate of another rate that is defined inside the object here.
In the latter case, the effctive accrual period and other conventions are governed by the Pre Fallback specifications, which supercede any similar specifications in OI Term Rate