code: public Collection<RegressionPlan> getRegressionPlans(RegressionPlanFilter filter, boolean includeSubprojects) {
          filter = (filter != null) ? filter : new RegressionPlanFilter();
  
          filter.project.clear();
          if (includeSubprojects) {
              for (Project project : getThisAndAllChildProjects()) {
                  filter.project.add(project);
              }
          } else {
              filter.project.add(this);
          }
          return getInstance().get().regressionPlans(filter);
      }
docs: A collection of regression plans that belong to this project.
  
  @param filter             Criteria to filter on. Project(s) will be set automatically.
  If null, all related regression items in the project are returned.
  @param includeSubprojects Specifies whether to include items from sub-project or not.
  This only adds open subprojects.
  @return RegressionPlan.