code: func (h *healthcheckManager) pruneMarks() {
  	h.lock.RLock()
  	checks := h.checks
  	h.lock.RUnlock()
  
  	backends := make(map[seesaw.IP]bool)
  	for _, check := range checks {
  		if check.key.healthcheckMode != seesaw.HCModeDSR {
  			continue
  		}
  		backends[check.key.backendIP] = true
  	}
  
  	for ip := range h.marks {
  		if _, ok := backends[ip]; !ok {
  			h.unmarkBackend(ip)
  		}
  	}
  }
docs: // pruneMarks unmarks backends that no longer have DSR healthchecks configured.