code: func (pq *txPriorityQueue) SetLessFunc(lessFunc txPriorityQueueLessFunc) {
  	pq.lessFunc = lessFunc
  	heap.Init(pq)
  }
docs: // SetLessFunc sets the compare function for the priority queue to the provided
  // function.  It also invokes heap.Init on the priority queue using the new
  // function so it can immediately be used with heap.Push/Pop.