code: function( origEvent ) {
              var prev = steps.indexOf( activeStep ) - 1;
              prev = prev >= 0 ? steps[ prev ] : steps[ steps.length - 1 ];
  
              return goto( prev, undefined, "prev", origEvent );
          }
docs: `prev` API function goes to previous step (in document order) `event` is optional, may contain the event that caused the need to call prev()