go to the DATA-LENS․TRANSDUCERS․INTERNALS∶∶REDUCE-GENERIC COMMON-LISP∶∶SEQUENCE COMMON-LISP∶∶FUNCTION COMMON-LISP∶∶T method (The data-lens/beta/transducers Reference Manual)
The node you are looking for is at go to the DATA-LENS․TRANSDUCERS․INTERNALS∶∶REDUCE-GENERIC COMMON-LISP∶∶SEQUENCE COMMON-LISP∶∶FUNCTION COMMON-LISP∶∶T method.