nl_tokens: A we don t know right now but hope to soon .
pl_tokens: function DeferredType ( typeSpec ) { if ( typeof typeSpec . defer !== 'function' ) { throw new Error ( 'Instances of DeferredType need typeSpec.defer to be a function that returns a type' ) ; } Object . keys ( typeSpec ) . forEach ( function ( <mask> ) { this [ key ] = typeSpec [ key ] ; } , this ) ; }