code: function addMarkers(fetchResult) {
                      var items = fetchResult.items,
                          offset = fetchResult.offset,
                          totalCount = fetchResult.totalCount,
                          absoluteIndex = fetchResult.absoluteIndex,
                          atStart = fetchResult.atStart,
                          atEnd = fetchResult.atEnd;
  
                      if (isNonNegativeNumber(absoluteIndex)) {
                          if (isNonNegativeNumber(totalCount)) {
                              var itemsLength = items.length;
                              if (absoluteIndex - offset + itemsLength === totalCount) {
                                  atEnd = true;
                              }
                          }
  
                          if (offset === absoluteIndex) {
                              atStart = true;
                          }
                      }
  
                      if (atStart) {
                          items.unshift(startMarker);
                          fetchResult.offset++;
                      }
  
                      if (atEnd) {
                          items.push(endMarker);
                      }
                  }
docs: Adds markers on behalf of the data adapter if their presence can be deduced