grails - liquibase groovy foreign key constraint -

let's assume i've got tables

book     id pk_id     name   library     book_id fk_book_id references book(id) ... 

i want add constraint name fk_book_id library table, foreign key, references id field of table book. how that?

column(name:'book_id'...) {     constraints {          nullable(false)         unique(true)     }     constraints(foreignkeyname: 'fk_book_id', references: 'book' ... ) // column? } 

i know addforeignkeycontraint method, i'd use constraints. syntax it?