go to the DATA-LENS․LENSES∶∶FMAP COMMON-LISP∶∶T DATA-LENS․LENSES∶∶IDENTITY- method (The data-lens/beta/transducers Reference Manual)
The node you are looking for is at go to the DATA-LENS․LENSES∶∶FMAP COMMON-LISP∶∶T DATA-LENS․LENSES∶∶IDENTITY- method.