mapper
inline fun <FromKey, FromValue, ToKey, ToValue> mapper(noinline keyFromToTo: suspend FromKey.() -> ToKey = { this as ToKey }, noinline valueFromToTo: suspend FromValue.() -> ToValue = { this as ToValue }, noinline keyToToFrom: suspend ToKey.() -> FromKey = { this as FromKey }, noinline valueToToFrom: suspend ToValue.() -> FromValue = { this as FromValue }): SimpleMapperRepo<FromKey, FromValue, ToKey, ToValue>(source)