code: List<PageEntry> getEntries(int firstIndex, int lastIndex) {
          Preconditions.checkArgument(firstIndex <= lastIndex, "firstIndex must be smaller than or equal to lastIndex.");
          ArrayList<PageEntry> result = new ArrayList<>();
          for (int i = firstIndex; i <= lastIndex; i++) {
              result.add(getEntryAt(i));
          }
  
          return result;
      }
docs: Gets all the Page Entries between the two indices.
  
  @param firstIndex The first index to get Page Entries from (inclusive).
  @param lastIndex  The last index to get Page Entries to (inclusive).
  @return A new List containing the desired result.