code: func (sh *GNDSignificanceHeuristic) BackgroundIsSuperset(backgroundIsSuperset bool) *GNDSignificanceHeuristic {
  	sh.backgroundIsSuperset = &backgroundIsSuperset
  	return sh
  }
docs: // BackgroundIsSuperset indicates whether you defined a custom background
  // filter that represents a difference set of documents that you want to
  // compare to.