nl_tokens: Create a yield () function tailored for this iterator .
pl_tokens: function ( expr ) { // Ensure this function is executing inside a fiber. if ( ! Fiber . <mask> ) { throw new Error ( 'await functions, yield functions, and value-returning suspendable ' + 'functions may only be called from inside a suspendable function. ' ) ; } // Notify waiters of the next result, then suspend the iterator. if ( runContext . callback ) runContext . callback ( null , { value : expr , done : false } ) ; if ( runContext . resolver ) runContext . resolver . resolve ( { value : expr , done : false } ) ; Fiber . yield ( ) ; }