package Ġco . nil in . op ex . matching . engine . core . spi Ċ Ċ import Ġco . nil in . op ex . matching . engine . core . model . Persistent Order Book Ċ Ċ interface ĠOrder Book Pers ister Ġ{ ĊĠĠĠ Ġsuspend Ġfun Ġstore Last State ( order Book : ĠPersistent Order Book ) ĊĠĠĠ Ġsuspend Ġfun Ġload Last State ( symbol : ĠString ): ĠPersistent Order Book ? Ċ }