code: func CheckRouteOverlaps(toCheck *net.IPNet) error {
  	if networkGetRoutesFct == nil {
  		networkGetRoutesFct = ns.NlHandle().RouteList
  	}
  	networks, err := networkGetRoutesFct(nil, netlink.FAMILY_V4)
  	if err != nil {
  		return err
  	}
  	for _, network := range networks {
  		if network.Dst != nil && NetworkOverlaps(toCheck, network.Dst) {
  			return ErrNetworkOverlaps
  		}
  	}
  	return nil
  }
docs: // CheckRouteOverlaps checks whether the passed network overlaps with any existing routes