code: public Collection<PrimaryWorkitem> getPrimaryWorkitems(PrimaryWorkitemFilter filter, boolean includeSubprojects) {
          filter = (filter != null) ? filter : new PrimaryWorkitemFilter();
  
          return getInstance().get().primaryWorkitems(
                  getFilter(filter, includeSubprojects));
      }
docs: Get PrimaryWorkitems in this Project filtered as specified in the passed
  in filter.
  
  @param filter             Criteria to filter on. Project will be set automatically.
  If null, all stories and defects in the project are
  returned.
  @param includeSubprojects Specifies whether to include items from sub
  project or not. This only adds open subprojects.
  @return An Collection of PrimaryWorkitem.