code: public List<ESigItem> findItems(ESigFilter filter) {
          List<ESigItem> list = new ArrayList<ESigItem>();
          
          if (filter == null) {
              list.addAll(items);
          } else {
              for (ESigItem item : items) {
                  if (filter.matches(item)) {
                      list.add(item);
                  }
              }
          }
          
          return list;
      }
docs: Returns a list of sig items that match the specified filter. If the filter is null, all sig
  items are returned.
  
  @param filter The esignature filter.
  @return List of matching sig items.