code: function( step ) {
              if ( typeof step === "number" ) {
                  step = step < 0 ? steps[ steps.length + step ] : steps[ step ];
              } else if ( typeof step === "string" ) {
                  step = lib.util.byId( step );
              }
              return ( step && step.id && stepsData[ "impress-" + step.id ] ) ? step : null;
          }
docs: `getStep` is a helper function that returns a step element defined by parameter. If a number is given, step with index given by the number is returned, if a string is given step element with such id is returned, if DOM element is given it is returned if it is a correct step element.