code: public Collection<PrimaryWorkitem> primaryWorkitems(
              PrimaryWorkitemFilter filter) {
          return get(PrimaryWorkitem.class, (filter != null) ? filter : new PrimaryWorkitemFilter());
      }
docs: Get primary workitems (stories and defects) filtered by the criteria
  specified in the passed in filter.
  
  @param filter Limit the items returned. If null, then all items returned.
  @return Collection of items as specified in the filter.